 |
Frequently asked Gardening Questions |
| Cochise County Cooperative
Extension Home Horticulture Environmentally Responsible Gardening & Landscaping in the High Desert |
|
| Please Note: To print out a question and answer highlight text and copy into your home word processing software or notepad. Otherwise the entire FAQ page will print which totals about 40 pages. |
|
Home | Back to Desert Gardening | Back to Newsletter
Question: My compost pile was doing very well, but after the recent rains we have had it really smells bad. What happened and what can I do about it? Answer: Your compost pile is to wet and therefore has very little if any air available to the organisms that break down organic matter in it. Anaerobic respiration or fermentation has taken over and is causing the bad smells. Control: Turn over the compost pile to get more air introduced into it. This will allow normal decomposition of the organic matter. Try and keep the compost pile as moist as a well-rung out sponge throughout the pile. In the desert the outside of the pile dries out quickly. Re-wet the surface every couple of days as needed. Back to Top
Question: Should I fertilize and water my outdoor plants during the winter? Answer: Fertilizing of trees and shrubs during the winter in the High Desert should not be done. Fertilizer could stimulate plants to come out of dormancy, start new growth and winter damage could occur. These plants are "resting" above the ground but do have activity in the roots if soil temperatures are warm. Normally trees and shrubs that go into winter with adequate soil moisture do not need watering during the winter. Usually winter rains or snow provide enough water. Deciduous plants do not need much water because the leaves, where transpiration occurs, are gone and nutrients needed for growth are not required because there is no shoot growth. The same holds true for most evergreen plants. When the air temperatures are cold and sunlight is reduced, why grow? However, if winter moisture is not sufficient to keep the roots moist they will die. If no winter moisture occurs for four to six weeks then water. Question: Should I fertilize and water my house plants during the winter? Answer: Houseplants are generally tropical in origin and survive best in warm humid environments. Houseplants need to be watered because of the limited soil volume they are confined to. House temperatures are warm and allow plants to continue to grow. The best way to determine soil moisture is to stick a finger in the soil one to two inches. If the soil feels dry, water; if soil feels moist, don't water. Fertilizing houseplants during in the winter months is not encouraged because of reduced light from the sun. However, if you are "spoon feeding" your plants, that is giving a little fertilizer at each watering, cut back on the fertilizer by giving 3 to 2 the normal amount. Many house plants need high humidity to be "happy", this is especially true with ferns. With forced air heating in many homes, house humidity can be lower during the winter than during the hot summer because of swamp cooler use. Humidity can be created by placing the potted plant on top of a pebble filled shallow dish. Fill the dish with water as needed, maintaining the water level near the top. The dish should have a diameter nearly as large as the plant diameter. The pebbles are import so that the potted plant is not sitting in water which will cause soil saturation, and thus root rot. As the water evaporates a humid environment is created in which a tropical plant will grow and thrive. This is much better than using a squirt bottle three times a day to try and humidify the plant! Question: How much fertilizer do shade trees need, what kind is the best, and when should it be applied? Answer: Ornamental trees and shrubs planted in fertile, well drained soil that are growing normally do not need extra nutrients. If they are not doing well fertilization may be helpful but only after the problem causing poor growth is corrected. Symptoms of poor growth may be light green or yellow leaves; smaller and/or fewer than normal leaves or dead spots; wilting of foliage; few flowers; short annual twig growth; and branch tip die back. These symptoms of poor growth may be caused by poor environmental situations like: inadequate soil aeration and moisture, or nutrition; adverse climatic conditions; wrong pH; or insects and diseases. Normally the only nutrient applied to established trees and shrubs in nitrogen. Other situations like chlorotic leaves, manifested by yellowing of leaves but veins remain green, require specific applications of a nutrient, in this case iron. The amount of nitrogen needed will depend on the size of the plant. Measure the diameter of the trunk about one foot from the ground. Apply 0.05 pounds of actual nitrogen/inch of trunk diameter. If a tree has a trunk diameter of six inches multiply by 0.05 to get 0.3 pounds of actual nitrogen. Divide the amount of nitrogen by the percentage of nitrogen content of the fertilizer to be applied. For example: 0.3 pounds of nitrogen applied as 21% ammonium sulfate would be: 0.3/21% = 1.43 pounds of ammonium sulfate fertilizer from the bag. Distribute the fertilizer evenly by measuring the distance between the trunk and drip line and multiply by 125%. This will determine the outer boundary radius for fertilizer application. Distribute the fertilizer evenly in the outer 2/3 of this circle. For example: If the trunk is eight feet from the drip line, then the outer boundary will be ten feet, (8 X 125% = 10). Apply fertilizer around the tree or shrub in a doughnut shaped band this 3.3 feet to 10 feet from the trunk, (10/3 = 3.3). Applications are best applied from early spring. Question: I am confused about fertilizers. What do the numbers on the bag mean? What are the differences between organic and chemical fertilizers? Answer: By law 3 numbers are required on a fertilizer bag. These are the percentage by weight of nitrogen (N), phosphorus (P) and potassium (K) or N-P-K in that order. Therefore, a bag of ammonium phosphate is marked 16-20-0 or 16% N , 20% P, and 0% K. The N is actual total N no matter what the form. P is really the percentage of P205 and K is really percentage of K2O. (A small side-note -- To get the actual amount of P you must multiply the number on the bag by 43% and by 83% to get the actual amount of K. These percentages are derived by taking the atomic weight of the element in question and dividing by the atomic weight of the molecule that the element is in. There have been efforts to revise the current labeling of fertilizers so that only the percentage of P and K appear, but these efforts thus far have ended in failure.) Our soils need N for normal plant growth. This is because it leaches from the root zone. N is absorb most of their N in the NH4+ ammonium and NO3- nitrate. These are both inorganic molecules. Generally plants use nitrate form over the ammonium form. Ammonium is converted to N in the soil by aerobic bacteria and some fungi, therefore cool, wet soils have less active bacteria and will yield less nitrate nitrogen. Nitrate forms of nitrogen are taken up by plants directly and is better used in cool, moist soils. Many nitrogen based fertilizers are made by a process which uses atmospheric nitrogen, the air we breath is about 78% nitrogen, and natural gas or methane under high pressure and heat. Organic forms of nitrogen must be mineralized that is converted into inorganic nitrogen by soil microorganisms for plant use. Also the carbonaceous material of the organic matter is broken down in to humus by soil organisms and use N as an energy source. Organic sources of nitrogen included blood meal which is usually around 15% nitrogen. Our desert soils are also low in native phosphorus and should be added at planting time. Phosphorus binds with the soil and does not leach or can not be "melted" into the soil with water like nitrogen. There are several forms of phosphorus many being produced by treating phosphate rock with an acid like phosphoric acid. This yield triple super phosphate or 0-45-0 on the fertilizer bag and can be neutralized with ammonia to make ammonium phosphate and liquid fertilizers. Organic forms of phosphorus are available with bonemeal, 0-12-0 being the most common. Potassium is not needed usually in our desert soils. There are many fertilizers on the market which have other nutrients for plant growth. Higher priced fertilizers have some of these nutrients added and increase the cost. Organic based fertilizers like manures and composts have lower plant nutrient levels but add organic matter to our soils and are more beneficial in this regard than chemically based fertilizers. However, the cost and high amounts needed of organic fertilizers for normal plant growth are very high when compared to bagged chemical fertilizers. Question: Surflan is called a preemergent herbicides. What does that mean, how and why are they used? Answer: Preemergent herbicides are a class of weed killers that are applied to the soil before weeds emerge from the ground. The activity of these compounds usually kill germinating seedlings before they emerge from the soil. The new roots and/or shoots absorb some of the material and the plants die. The herbicides are applied to the soil and are usually incorporated into the soil by tillage or irrigation after application. This is necessary because environmental factors such as sunlight cause these products to degrade over time. With pesticides there are several names of each compound that must be understood to avoid confusion. For a single pesticide compound there are three classes of naming. The first is the long chemical name from which a good chemist can reconstruct the molecular structure. The second is the common name, which is registered and approved by the EPA, and is peculiar to that compound no matter who is manufacturer. This common name is analogous a scientific or Latin name of a plant. The third name is the trade name. This name is copyrighted by the seller, but the same chemical can have many trade names. Similar to common plant names. After patent rights expire on the compound anyone can manufacturer the chemical and give it any name they choose. All of this information is found on the label by law. For example a common preemergent herbicide has a chemical name of: 3,5-dintro-N4, N4-dipropylsulfanilamide. The common name is oryzalin. Some trade names are Surflan, (this is the name that the manufacturer uses), Monterey Weed Stopper, or Weed Blocker. The manufacturer sells this compound to others who package Surflan in smaller home use size containers and give their packaged material another name like Monterey Weed Stopper. Surflan and several other preemergent herbicides are yellow to orange in color. This is because they were synthesized and discovered they had herbicidal activity by the dye industry. Surflan for example is bright orange. When it is being applied by city employees, for example, on median islands or in park landscapes people have become irritated thinking they were using "Agent Orange"! This is not the case. The two are not related. The best time to apply Surflan herbicide in the landscape is in the spring and/or again in the fall. Surflan persist from four to six months depending on environmental conditions. It works well over crushed granite or gravel that does not have plastic under it. Surflan can also be applied to lawns, flower beds (where flower seed is not planted) or transplanted through. Surflan must be watered in within 30 day or it is broken down by sunlight. Here in the high desert it is best to get it watered in with in the first week. With proper and timely application a "weed barrier" is formed and many grasses and broadleaf weeds will be controlled. As with all pesticides read the label and follow all instructions. Back to Top
Question: There are small, sunken, brown spots on the Golden Delicious apples I picked. When I cut in these spots the tissue is brown and corky. What pest causes this problem? How can I control it? Answer: The problem you are seeing is called bitter pit. This is not caused by a pest but rather a deficiency of calcium, causing cell walls to not form properly. Bitter pit is increased by nutrient imbalances, hot weather conditions, and orchard practices. The tendency for bitter pit to occur increases as the ratio of potassium and magnesium to calcium increases. Other factors include excessive tree vigor, light crop load, or excessive thinning. Control: Bitter pit can be decreased by minimizing or avoiding
excessive tree vigor, caused by over fertilization, harvesting only mature
fruit, regular watering, and maintaining a proper fruit load. Foliar sprays of
calcium can reduce bitter pit in fruit. Bitter pit can appear while the apples
are still on the tree or during storage. Cool the fruit rapidly after harvest.
Storage at low temperature and in high relative humidity conditions can also
reduce the development of this disorder in stored fruit. The fruit is still good
to eat but the bitter pit areas may impart a slight bitter taste. Question: I have apple, peach and plum trees were planted in 1963. They are being attacked by a boring insect that makes trails under the bark. What can I do to get rid of these insects? Answer: There are several insects that will bore into and make galleries under the bark. These insects however for the most part attack only weak growing or old trees. The trees are nearly 34 years old and fall into the weak and old tree category. Generally fruit trees if cared for will live for 25 to 35 years. There are some exceptions like pear and apricot trees. I would not spend a lot of time on these trees that naturally declining anyway, other than taking them out and replacing them. I would plant some new fruit trees if you want to harvest fruit over the next few years. Question: How can I tell if my apples, pear, peach, cherry and apricot flowers suffered freeze damage from freezing temperatures? Answer: Most of the fruit mentioned will freeze if in full bloom during temperatures from 23 to 28E F. To examine a flower or fruit remove one from the tree. Make a horizontal cut with a knife through the base of the flower just beneath where the flower petals are attached. If small fruits have already formed cut horizontally through them also. If the center of flower or fruitlet seed tissue, is brown in the center then the flower or seed(s) is/are dead. If the flower or seed tissue is green they are alive. If the seed(s) die then the hormonal stimulus that the seed(s) produce which signals fruit growth will not occur; therefore no fruit will be produced. Go around each tree and cut 10 or 20 flowers or fruitlets to determine the percent of survival. If only 5 to 10% of peach flowers survived there will be a crop. If only 10 to 20% of apple or pears survived you will have a full crop. If more survived you will probably have to thin the fruit in a few weeks to produce large fruit. If thinning is not done either by man or Mother Nature's freezes small, inferior fruit will be produced. Question: I have noticed small holes in the bark of my apple, cherry, peach, plum and mulberry trees. It looks as if the trees have been shot with a shotgun. The stone fruits have gummy material coming out of the holes. What is the cause of these holes and how can I control it? Answer: The holes you see are caused by shothole bores, (Scolytus rugulosus (Müller)). Shot hole bores are beetles that were introduced from Europe in 1878. They can be destructive pests of fruit and ornamental trees, and shrubs. Numerous small "shot holes" are seen in the bark of twigs and branches. The gummy exudate from the stone fruit trees is their response to try and fend off the invaders. The adult beetle is 2.5 mm or less in length, brown-black, with a short stubby snout with chewing mouth parts. The thorax is shiny and elongated, the elytra, or wing covers are dull. Adults burrow through the bark and live between the bark and sapwood of the plant. Adult feeding excavates narrow galleries running parallel to the wood grain under the bark. Eggs are oval to round and pearly white in color. Females lay 50 eggs in niches along the gallery she has made. As the eggs hatch the larvae excavate slender mines or burrows, usually at right angles to the maternal gallery, occasionally crisscrossing over one another between the bark and sapwood. The larval burrows are filled with excrement and grow wider as the larvae grow. They become fully grown six to eight weeks later and construct pupal cells at the ends of the mines. Upon completion of pupation young adults burrow through the bark to the outside world, mate, and the cycle starts anew. The larvae of the last generation of the year complete development during late winter and early spring as temperatures rise. In Southern Arizona there are normally three generations per year. Control: Healthy, vigorous, well-cared-for trees are less subject to attack by shothole borers. Plant maintenance through correct watering at the drip-line, proper fertilization, and pruning practices keep trees healthy. Affected branches should be pruned out burned to decrease insect populations. Plants receiving a regular spray program are not troubled by shothole borers. Sources: Orchard Pest Management. Elizabeth H. Beers, et al., Editors. 1993. Good Fruit Grower. Yakima, WA. Pages 186-187. Insect Pests of Farm, Garden, and Orchard. Ralph H. Davidson and William F. Lyon. 1987. John Wiley & Sons, Inc. New York. Pages 404-405. Question: I have a pear, apple, peach, nectarine, plum, apricot and cherry trees which have new leaves that are curling up around the edges and are deformed. Is this peach leaf curl? Answer: Peach leaf curl is caused by a fungus and does not affect pear and apple trees. The problem at hand is caused by the western flower thrip or onion thrip. Thrips are small, 1/25-1/50th inch long or so, and lay their eggs in flower or leaf buds or on very young leaf tissue. They feed with their rasping sucking mouth parts and cause irreversible damage to the plant tissue, flowers and fruit. Five to 15 generations per year can be produced. To see if you have thrips hold a piece of white paper under the damaged leaves and tap them sharply. Thrips will fall on the paper and start to walk around. They rarely fly because they are weak flyers but will hop. There have been vast numbers of thrips this year because of the good winter rains we had which caused cool season weeds, mustard particularly, to thrive. Thrip populations build up to high levels on these weeds and when they die down, due to warm weather, the thrips migrate to fruit trees, roses and other perennial flowers. Control: Thrips are hard to control once they are inside a bud because they are protected. Systemic pesticides do help with thrips on roses, peonies and other perennial flowers. Hang up blue or yellow sticky traps to catch adults as they move into an area. Diatomaceous earth applied to the underside of the leaves my also be helpful. As a last resort sprays of insecticidal soap, rubbing alcohol or other insecticides may be helpful. The best thing to do is control weeds where thrips are living in the early spring. Annually check weeds on your property to see if thrips are there. Us the method described above. Generally plants will out grow the damage caused by thrips by producing new leaves, but damaged leaves flowers and fruit will not be mended. Source: Carr Anna et. al. Chemical-Free Yard and Gardening. 1991. Rodale Press, Inc., Emmaus, PA. pp. 242, 244. Question: I have a pear tree that has some bumps on the leaves. Over time the bumps turn into brown spots. Is this zinc deficiency? Answer: No you do not have zinc deficiency. The damage you see is caused by mites, most likely the pearleaf blister mites (Phytoptus pyri Pagenstecher). This mite was introduced from Europe, probably before 1900. It is a pest of most pear growing areas of the world. Feeding by these mites causes damage on leaves and fruit. Blister mites overwinter as mature females at the base of buds or under outer bud scales. Adults are light to amber yellow in color and cylindrical, tapered sharply at the posterior end and resemble a short worm. In spring, when buds begin to swell, overwintering females penetrate deeper into bud and lay eggs on live tissues. Development from egg to adult requires 20 to 30 days during spring. Feeding of females and their offspring causes blisters on developing leaves. Blister are green or red at first but turn light brown to black as affected tissue dies. As the blisters form, leaf cells near the center of the blisters die and pull apart as surrounding cells enlarge, creating a hole. Blisters vary in size, with the largest about 1/8 inch in diameter. Mites do not live in the blisters on the fruit, but the fruit will be scarred. Mites of the first spring generation enter blisters through these holes and feed on soft leaf tissue inside. Several generations develop within the blisters during a growing season. Summer generations require only 10 to 12 days to develop. When blisters become crowded or leaves become heavily damaged, mites may migrate to growing terminals where their feeding produces new blisters. Fruit damage is caused by injury to buds before bloom. Severe damage to foliage can cause leaf drop and reduce shoot growth. Look at young leaves before bloom early in the spring just as leaves are unrolling. Noticeable light green to light red rough areas where mites have been feeding will be seen. This damage becomes more noticeable as the growing season progresses. Control: Blister mites are not normally controlled by natural enemies. Predatory mites will feed on blister mites when they are exposed. Blister mites often attack weak, neglected or abandoned trees. If a pesticide is used to control blister mites the best timing is after harvest when mites migrate from leaf blisters to terminal and fruit buds. They are exposed on those sites until buds swell in the spring. Pre-bloom treatments can prevent fruit damage that occurs just before and during bloom. Source: Orchard Pest Management. 1993. Edited by: Elizabeth H. Beers, et al. Good Fruit Grower Publications, Yakima, WA. Pages 151-153. Question: I have several twelve-year-old cherry and peach trees that have holes in the leaves. Also some of the cherries have a greyish spot forming on the fruit. I do not see any insects. What is causing the holes and what can I do about them? Answer: It sounds as though your trees are affected by bacterial canker of stone fruit or Pseudomonas syringae. Other common names include gummosis, blossom blast, die back, spur blight, and twig blight. There are several different races of this bacteria. Symptoms may appear on some trees and not on others. These include canker development on twigs at the base of flower and leaf buds, and the base of spurs. Cankers normally spread upward, and the infected sunken areas are usually formed in late winter or early spring. Gum often exudes from the canker during the early part of the growing season. If the canker girdles a limb it will die in short order. However, the root system stays healthy and may even produce sucker growth. Dormant leaf and flower buds may be infected and are often killed, but some invaded buds develop normally but will collapse in early summer. Leaves and fruit produced by these buds wilt and dry out. In contrast, leaves and flowers of other infected buds will remain symptomless. Leaf infections especially on cherries appear as water-soaked spots that later become brown and dry. At a later stage shot holes may be seen on leaves sporadically and not always symptomatic of the disease. Control: Make sure that the trees are pruned, watered and fertilized
properly. There is some indication that during mild, wet winters bacteria
populations can increase. Trees are particularly susceptible in sandy soils,
water logged soils that drain poorly, and during prolonged drought periods.
Careful watering is a must. Precautions should be taken while pruning not to
spread the disease. Dipping pruners in 20% bleach solution after each pruning
cut should help. Chemical control of bacterial canker is based on protective
copper containing sprays applied in autumn and spring before flowering. In
cherry and peach growing area there are strains of bacterial canker that are
resistant to copper sprays. Question: My apple tree has branches that are dead or dying. Leaves are drying up and the bark is sunburned. What can I do to stop this? Answer: What you are seeing are the symptoms of a problem in the root system of the apple tree. It could be a soil born fungus like phytophtera, but is more likely to be a ground dwelling insect pest called a wooly apple aphid, (Erisoma lanigerum). Also pears are injured by the wooly pear aphid, (Erisoma pyricola). These aphids are native to the eastern United States and Canada, but is a worldwide pest that attack elm, mountain ash, and some species of hawthorn trees as alternate hosts. A fluffy white wooly covering over most of the insect's posterior end of their blue black bodies and accounts for its name. This cottony looking substance can be seen in small masses on branches and shoots where injuries or pruning cuts have been made, as well as on roots. The life cycle of these insects is rather complicated. Females lay eggs on the bark of host or alternate host trees in the late summer or fall. These eggs over winter and hatch in the spring as wingless parthenogenic, (development from an unfertilized egg), females produce ovoviviparous, (eggs hatch within the females body), stem mothers which establish colonies on the terminal leaves. These leaves soon become curled and stunted from feeding. By early summer winged forms appear and fly to other apple trees or hosts to establish new colonies. Repeated generations are produced during the summer. Some of the individuals may crawl to the roots where they continue to reproduce indefinitely. In the fall, winged individuals develop again and fly to hosts and give birth to sexual forms which eventually mate and lay over wintering eggs. Not all aphids leave the apple trees, some wingless forms remain all winter, both above and below ground, thus maintaining a continuous infestation year around. On the roots nodules are formed from the insects feeding. These nodules are rough and bumpy looking and restrict the flow of water and nutrients from the roots to the leaves. Small leaves form and eventually the bark becomes sunburned and dried out and limbs die over several growing seasons. Control: When planting apple trees semi-dwarfing and dwarfing rootstocks with MM before the rootstock number should be used. Example: MM106 or MM111 are semi- dwarfing rootstocks which are resistant to the wooly apple aphid. The MM stands for Malling-Merton which are agricultural research stations in England which developed these rootstocks. Currently chemical control is the only means available to control wooly apple aphid. However, BioLogic Company, a bio-engineering firm has developed a parasitic nematode, (Steinernema carpocaposae), that has been 80% effective in controlling the ground dwelling form of this pest. They are not yet marketing the nematode. Chemical controls include dimethoate, (Cygon), a systemic insecticide. Other organic and chemical based insecticides that control aphids will control the above ground generations of this insect when they are in the tree, though the ground dwelling forms will not be affected. Source: Insect Pests of Farm, Garden, and Orchard. R. H. Davidson and W. F. Lyon. 1979. 7th Ed. pp. 392-393. John Wiley and Sons, New York. Question: I have a Golden Delicious apple tree with irregular large spots on the leaves. In some places the spots are turning brown and dying. Some of these affected leaves are falling to the ground. What is causing this and what can be done to stop it in the future. Answer: The apple tree is experiencing necrotic leaf blotch, also called leaf spot or leaf drop. Golden Delicious is particularly susceptible and this condition is restricted to this cultivar and others with its blood-line. This disorder is characterized by irregular necrotic blotches in mature leaves that develop rapidly, usually within 12 to 24 hours. The leaf first turns pail green and yellow, then darkens to a deep brown. The size of the affected area remains constant once visible symptoms appear. The size of the necrotic area is restricted by larger veins, which are not affected. Mature leaves, in the mid-shoot region, are usually affected first. Young vigorous trees appear less severely affected than older, more slowly growing trees. Leaf fall can be rapid once symptoms occur, sometimes within 4 to 7 days. Severity of the disease varies greatly from year to year. Variation can be great among trees in the same orchard or yard. Necrotic leaf blotch is a physiological disorder related to air temperature, light intensity, and soil moisture. It is most severe when a cool, rainy period of 4-5 days precedes several hot, sunny days. A hormonal imbalance is thought to be the cause, since symptoms are enhanced by gibberellin, (a plant hormone that is needed for cell enlargement); and inhibited by abscisic acid (another plant hormone that causes leaf and fruit fall). Control: Zinc oxide, applied every two weeks from bud break until harvest is effective in reducing disease incidences. Also, healthy, vigorous trees produced by good watering, fertilizing, fruit thinning, and pruning practices contribute to decreased incidences of necrotic leaf blotch. Source: Compendium of Apple and Pear Diseases. 1991. The American Phytopathological Society. Page 88. Back to Top
Insects & Pests Please Note: For insects, pests & diseases on plants please go to plant category Question: What can I do about cicadas? They are so loud some years? Answer: Periodic cicadas are distributed widely throughout the United
States. The annual cicadas are present in summer, but the periodic species have
long life cycles. A mature annual species is over two inches long, with a
brown-black body, ornamented with clear wings that have green veins. Eyes are
red to brown and quite large. There are six species of periodic cicadas in the
United States. Three with a 17-year life cycle and three with a 13-year life
cycle. When all life cycle coincide the male mating sounds can be deafening.
Damage is caused by egg laying or ovipostiting females in twigs and branches of
trees and shrubs. Branches having a diameter slightly larger than a pencil are
preferred. A series of wounds are made in which eggs are laid. Weakened branches
can break off or become permanently scarred and abnormal. Over 500 eggs can be
deposited by one female. Nymphal cicadas hatch and then drop to the ground,
burrow in to the soil, and feed on root sap. Depending on the species they will
remain in soil for 17 or 13 years. At the end of this time they emerge from the
ground through soil tubes they construct that are nearly a half an inch wide and
a quarter inch high above the ground. Great numbers emerge at the same time,
starting at dusk. They crawl up tree trunks or other objects, expand their
wings, and begin their short adult life. The familiar song or call is made only
by the males and is produced by a pair of drum like organs on the basal segments
of the abdomen. These love calls can become very loud. Mating occurs and then
egg laying begins, completing the life cycle. Question: I have a lot of grasshoppers in my yard. They are eating everything! How can I control them? Answer: In Cochise County we have several species of grasshoppers, some are very colorful and grow quite large. Grasshoppers emerge in the spring from eggs laid last year. Grasshoppers hatch as miniature adults and molt 5 or 6 times during a period of 40 to 60 days. The young feed in the immediate vicinity and then move on to "greener pastures" as food sources become depleted. Adults begin laying eggs shortly after they mature. Eggs are laid in the ground in pods that contain 15 to 75 eggs. A female can lay a total of 200 to 400 eggs during several weeks. Hatching rate depends on soil temperature and moisture and may continue for 3 months. Some species have more than one generation per year. Grasshoppers feed on grasses and other plants. When populations increase they will feed on nearly any kind of vegetation including bark and leaves of deciduous trees. Adults continue to feed until cold weather kills them. Natural weather cycles cause fluctuations in populations. Mild winters and warm, dry springs increase hopper populations. Cold, wet weather cause slow development and favor grasshopper diseases. Cool summers and early falls delay maturity and decrease the egg laying period. Control: If desert surrounds your property it can become very difficult
to control grasshoppers because of large populations that can become migratory.
Disturbing egg pods in the soil by tilling or plowing will expose egg pods,
decreasing their viability. Young small hoppers are easier to control than
adults. "Picking and squashing" is a time consuming but effective
control measure. Several chemicals insecticides will control grasshoppers as
well as the abrasive nature of diatomaceous earth. Nosema locustae is a
naturally occurring disease organism of grasshoppers. Bran and sweeteners are
added to Nosema to attract the hoppers. Grasshopper are cannibalistic and
infection spreads as healthy hoppers eat sick ones. Also the females pass this
disease on to future generations through laid eggs. Nosema will take longer to
destroy grasshopper populations than conventional pesticides. This is a living
organism and must be stored in the refrigerator and has a limited shelf life.
Contact your local nursery or garden catalog for current recommendations. Always
read the label of pesticides and use them accordingly. Question: I see some bees coming around my hummingbird feeder. Is it possible these are the "killer" bees that have killed dogs and attacked people? Answer: There is no way of knowing if the bees you see are the Africanized Honeybee (AHB). Visually EHB and AHB are identical to each other. Experts can not tell them apart with out laboratory analysis. They are not killer bees, even though the media makes it sounds as if these insects require human flesh to complete their life cycle! Honeybees are not native to the Americas. There are six species of honeybees in the world and over 20,000 known species of bees. European Honeybees (EHB) were brought to America by immigrants and known by Native Americans as white man's lice. In the mid 1950's bee researchers imported some AHB into Brazil to breed with EHB to hopefully increase the EHB's honey production in tropical environments. Some AHB escaped and began moving north. They arrived in south Texas 1992. Honeybees defend there colonies or home vigorously because this is where their young are reared and food is stored. In nature bears, skunks and other animals try to steal their stored food. Honeybees are aggravated by motions of larger dark objects, animal smells like leather and perfumes, shampoos and perspiration. Both bee species sting in the same way, going for the head and eyes, with a barbed stinger that remains in the victim. AHB venom is just as potent as EHB venom. Venom is pumped from a bulb on the top end of the stinger through it into flesh. Stingers should be scraped out with a knife, finger nail or credit card. Trying to pull out a stinger will squeeze more venom into the victim's flesh. A lone foraging bee whether an EHB or AHB will not bother you if you do not bother it. Swarms of honeybees are seen during the spring and summer and with AHB swarm even in the fall and warm winters. About half of the old colonies bees accompany the queen. This is the way that honeybees divide and establish colony and form another. They are not defensive because they are looking for a home and have nothing to defend. Once a place is located by scout bees and the swarm then set up house keeping. When the new colony is established with young and food stores the bees will defend it. AHB will defend their colony more vigorously than EHB. EHB have been selected and red for centuries to be docile and productive. AHB are just like EHB but just have a bad aggressive attitude. More people die in the United States from lighting than from bee stings. The numbers perhaps will increase with the AHB but will not likely surpass lightning deaths. It is advised to close holes and cracks in homes, barns and out-buildings that are larger than a pencil eraser. Use caulk, boards or other suitable materials. Make weekly inspections of wood piles, abandon cars, old tires and junk piles which could make suitable place for swarming bees to establish new colonies. If new colonies are found call certified bee removal personnel such as beekeeper, pest control operators or the Arizona Department of Agriculture so action can be initiated. If you or someone else is stung run into a house or vehicle to get away from other bees. A sting pheromone alerts other bees to sting also. Do not swat at the bees with your hands and arms just run to safety. If you are out in the open you must run for a quarter or half mile to distance yourself from the bees. We will have to learn to live with AHB but there is little difference from EHB. Question: How can I rid my property of gophers? They are making mounds and destroying some trees and bulbs in my garden. Answer: Pocket gophers are burrowing rodents. So named because they have fur-lined, outer pouches on each cheek, that can be turned inside out to carry food. Pocket gophers are strict herbivores and any animal material in their diets appears to be accidental. These rodents feed on roots, bulbs, corms or rhizomes they encounter when digging. They can pull vegetation into their tunnels from down below. They will also venture out of their runs a body length or so into the open to feed on above ground plant material. Pocket gophers burrows are a system of tunnels totaling up to 200 yards with densities of 6 to 8 rodents per acre a high population. The main burrow is generally 2 to 3 inches in diameter, depending on the size of the occupant and is 4 to 18 inches beneath the soil surface depending on the soil type. Lighter textured sandy soils will have deeper burrows than heavier clay soils. The soils ability to withstand cave-ins determines burrow depth, although some parts of the burrow maybe 5 to 6 feet deep. Deeper branches off of the main burrow are used for nests and food caches. Enlargements along the main burrow are usually feeding and resting stations. Nests chambers are lined with dry grass and other plant materials. A less apparent requirement of burrow depth is the need for fresh air and exhaled gases to pass through the soil to and from the gopher's tunnel. Therefore, heavy clay soils or those that are continuously wet, diffuse gases poorly and are not suitable for gophers. The fan shaped mound of soil seen on the surface is the excavated soil that is pushed out of the main burrow through a lateral branch. Pocket gophers are usually solitary except during the breeding season. Gophers have 1 or 2 litters per year and average 3 to 4 babies per litter, but 1 to 10 may be born. Birth is usually from March through June, after 18 or 19 days of gestation. Predators of pocket gophers that pursue them underground are weasels, perhaps spotted skunks and several snakes including bull and rattlesnakes. Dogs and cats may dig or capture them above ground along with other similar wildlife. Control: Exclusion cages may be made by using 1/4 to 1/2 inch mesh
hardware cloth which are placed in the ground and planted into. Plastic netting
placed under newly planted seed beds or bare root plants may slow gophers down.
There are no registered chemical repellents other than moth balls which are
ineffective. Also noise devices and plants reported to repel pocket gophers have
proven to be ineffective. Gopher traps are effective if a gopher runs into one.
They are placed in the burrow and should have a wire or twine tied to the trap
and an above ground stake so it can be retrieved when a gopher is caught.
Perhaps the best way to rid your garden is to use toxic baits. These are usually
grains that have be coated with poison. Currently the anitcoagulant
chlorophacinone formulated with a 0.005% active ingredient is available. This
product is placed on grain and then formed in to small bars which are held
together with a waxy material. Another poison is zinc phosphide, (2% active
ingredient), is also available as a grain bait. The best way to find the burrow
is with a pointed steel rod cane that is used by probing the area a foot or two
away from a mound. Remember that the mound is a short lateral tunnel off of the
main burrow where soil is removed from the burrow. When a burrow is found the
rod will go easily through the soil. Dig down to the tunnel, locating the burrow
hole on each sides of the hole you dug. Place some bait in each burrow hole and
cover the baited burrow hole with a weed or grass so that backfill soil will not
fall on top of the bait. Fill in the hole and then knock down any of the soil
mounds within a 10 to 15 foot radius of where you dug a hole. Come back in a
week and see if there are new mounds and bait those. Over time you will get the
pocket gophers under control. Question : We are having problems with deer eating leaves and shoots on our fruit trees. We have a 4 foot high fence which obviously is not high enough to keep them out. I've been thinking of installing a one or two strand electric fence above the existing one so the fence is about 6 or 7 feet high. I have also heard about baiting the electric fence to train the deer to keep away. Do you have any advise on this subject?Answer: Yes, a taller fence can keep out most deer. Deer will also crawl under fences if not close to the ground and secure. Deer have hollow hairs that do not conduct electricity and so they do not get shocked by electric fences. You can train them however. The most effective way that I know of is by making 2-3 inch wide strips of aluminum foil and maybe a foot long. Heavy duty foil is the most robust. Fold the foil over the wire and staple the strip ends together. Place some peanut butter on the foil. Place these "training devices" every 20 feet or so a long the fence. Electrify the fence. Because of the dry conditions we are experiencing there is a lack of native vegetation. Hunger and thirsty wildlife will take chances they normal would not while looking for food and/or water. If you create a garden oasis in the desert you will have more wildlife pressure during drought conditions. Question: What is chewing out perfect circles on the leaves of my plants? Answer: This is the work of the Leafcutter Bee (Megachile sidalceae). Leafcutter bees are solitary, small bees with black or gray bodies with white hair forming bands on the abdomen. Females cut out plant material from roses, ash, redbud, and other plants with smooth leaves. She uses the materials to construct cells and gathers pollen and nectar to make bee bread for the cell. She then lays eggs on the bee bread and closes the cell. Although unsightly, the damage leafcutter bees do to plants is cosmetic and will not kill the plant. No control is necessary. Bees are very important pollinators. Insects and animals pollinate over 70 percent of crops that we rely on for food, fibers, and medicines and 90 percent of landscape flowering plants, shrubs, and trees. Bees foraging for nectar and pollen in the garden are harmless and will not sting unless provoked to do so. Question: There are hundreds of thousands, perhaps even millions of insects that are long and black with grey spots that look like beetles have been swarming onto our property. They have been stripping our trees and vegetable garden with their voracious appetites. What are these insects? We have sprayed them and they die quite easily. What can we do about them? Answer: What you have experienced are blister beetles. In particular the spotted blister beetle, Epicauta maculata, according to my reference books. There are other types of blister beetles that have stripes or are solid black in color and even a metallic Arizona blister beetle. Blister beetles are elongated beetles 3/8" to 1 1/8" long. Their broad head is usually wider than their prothorax and connected by a narrow neck. The wings and body are soft and frequently the tip of the abdomen is exposed. Eggs clusters of up to 100 are laid in holes in the soil and hatch in 10 to 21 days. Larvae burrow in search of grasshopper eggs, pupate in 2 weeks, and over winter in the soil. Larvae are beneficial. One larvae can destroy 30 or more grasshopper eggs, which is the total laid by a single grasshopper. The active parasitic larvae can gain access to bee nests by attaching themselves to foraging bees. Adults of the several species have similar habits. They appear in the late spring through summer. The entire population will emerge in a very short period and forage on many different host plants. They feed on foliage, usually in large numbers, and after defoliating a plant will migrate to others. Usually only one generation is produced each year. All species contain a blistering substance, cantharadin. This material is extracted from a species in southern Europe, the Spanishfly, and used as a drug. Some species will secrete blistering materials or oily substances as a defensive action. Sometimes alfalfa hay that is bailed will have large populations in it and when eaten by livestock can cause blisters in the mouth and on the tongue, causing sores that will cause animals to stop eating because of the pain. Sources: How to Know the Insects. 1978. Roger G. Bland and H.E. Jaques. Page 223. Insect Pests of Farm, Garden, and Orchard, 7th Edition. 1979. Ralph H. Davidson and William F. Lyon. Pages 265-266. Question: We have just moved into a home that was not lived in for several months. There are several centipedes in the house. What can we do to get rid of them? Answer: The giant desert centipede (Scolopendra heros) are native to our high deserts. They are multi-segmented, elongated arthropods that have a distinct head and one pair of legs per body segment. They are flattened, fast moving predators, and generally brownish-yellow in color. Centipedes are 2.5 to 25 centimeter or more in length, with 10 to over 100 legs depending on the species. The giant desert centipede has a "pseudo head" for a tail which mimics the head in look and movement when preyed upon. This presumably will give the animal a fighting chance when attacked by birds, bats or other enemies. These critters hide in cool places- under rocks, boards, loose bark or in other dark moist places during the day. They actively seek prey at night, stunning or killing it with modified legs, called gnathopods, that are equipped with a poison gland. Their prey are insects and other arthropods, and in the case of the giant desert centipede small mammals or birds also. Their bite is not mortal to humans but is painful, similar to a wasp sting. Control: If a centipede is found in the house capture it in a box, bag or sack using gloved hands, a stick or tongs for guidance. Release it outside where it can prey on other insects like cockroaches. Sealing up the house, particularly outside door thresholds or holes where pipes enter the house, should prevent this beneficial arthropod from entering your living space. Source: Venomous Animals of Arizona. 1992. Robert L. Smith. The University of Arizona Cooperative Extension, Tucson, AZ. pp. 24-26. Question: What are these red fuzzy bugs that are climbing on my lawn? They have white markings on their backs and eight legs and are from 1/8th to nearly a 2 inch long. Do they harm my ornamental plants? Answer: These "bugs" are really spider mites. They are not bugs but rather arachnids or members of the spider family which have four pairs of legs, two body parts, no antenna and piercing, sucking mouth parts. These are the largest spider mites in our area. Most spider mites are quite small and a hand lens is needed to even see and identify them. Control: The red spider mite is a general feeder and usually does not cause excessive damage on plants. If they do, you can destroy them by stepping on them or spraying with insecticidal soap. Back to Top
Question: When should I dethatch my lawn? Answer: It depends on the type of lawn you have. Dethatching is done with either a machine rented from a rental shop or with specialized rakes that give the user a very good workout! Dethatching is done to remove excessive build up of plant materials that lies just beneath or just on top of the soil. The former are rhizomes and the later stolons. Stolons are stems that "creep" on top of the soil and rhizomes are underground stems. Both serve as sites from where new grass plants are formed. Dethatching is not for the removal of built-up grass leaf blades in the sod. These normally decompose naturally. Fescue type lawns do not have rhizomes or stolons and are never dethatched. Bluegrass has only rhizomes. These are cool-season plants and grow best with cool temperatures. Burmudagrass can spreads by means of seeds, rhizomes and stolons and is a warm-season grass, growing best in warm weather. Dethatching is a damaging procedure and should be done only when plants are vigorously growing and have plenty of time to recover from the damage caused by the machine or rake. Therefore, dethatch burmudagrass lawns about a month after it is growing well, normally the end of May or June. Bluegrass is rarely in need of dethatching but if need should be done in later September or October. Fescues never need to be dethatched because they do not produce stolons or rhizomes. Question: When is the proper time to plant a turf lawn? Answer: Because of our climate in Cochise County we can grow two general classes of turf. They are warm season and cool season grasses. Warm season grasses are those that flourish during spring and summer and then go dormant (brown) in the fall and winter. Warm season grasses include bermuda, buffalo grass, grama grass, sideoats, St. Augustine and zoysiagrass. These grasses should be sown, plugged, stolonizing or sprigging, (planting shoots with leaves) or sodded in the spring when temperatures are warming up. Cool season grasses grow best during cool weather but are green during the heat of summer if they are watered. They will remain green if winters are mild. Cool season grassed include Kentucky bluegrass, the fescues and ryegrasses. Cool season grasses are best sown or sodded in the late summer (late August or September) or early fall. The second best time to plant or sod these grasses is in early spring. Question: When should I plant native warm season grasses and how should I prepare the soil? Answer: Warm season native grasses include but are not limited to the bluestems, buffalos, gramas, Indian rices, lovegrasses, sideoats and wheatgrasses. Planting of most of these grasses should occur just before the monsoon rainy season begin in July. Seeding rates vary between different grass species. For example Buffalo grass is seeded at 3 to 4 pounds and blue grama grass is seed at 1 to 2 pounds per 1,000 square feet. In most situations it is advisable to mix 2 or more compatible species together and sow them so there is more diversity in the planting. For best germination and stand till the soil 4 to 6 inches deep, (this is very necessary on new construction sites because of compacted soil), rake smooth, spread seed, and top dress with compost or composed manure. The dark compost will warm the soil and hold moisture which aids in germination. Many of these warm season grasses make attractive landscape areas but are not suited to heavy traffic and play. However, breeding programs are currently developing turf type lawn grasses from native warm season grass species that will withstand traffic. Also, many of these grasses are more drought tolerant than the more traditional turf grass and require less water than bermuda grass. Question: Last year my bermuda grass lawn seemed yellow in the spring so nitrogen fertilizer was applied. The lawn looked better but later in the summer it looked yellow again. Nitrogen was applied but the lawn was still yellow. Why did the spring application of nitrogen work and the summer application did not? Answer: Nitrogen is needed for fast spring growth. Iron becomes less available in alkaline soils as the season progresses. Nitrogen deficiency shows up in older leaves that are yellow. Plants can break down nitrogen containing compounds and move it where the greatest need is, normally growing points, leaving older tissues yellow. On the other hand iron is used by plants to produce several compounds including chlorophyll. Plants can not broken down iron and moved it to other parts of the of the plant. As the growing season progresses alkaline soils bind iron and it becomes less available. So new leaves become chlorotic. Iron chlorosis has visual symptoms of green veins on new leaves but the interveinal spaces are yellow. Excessive watering can also cause iron chlorosis because soil oxygen pore space is filled with water. No oxygen- no root growth and little if any iron uptake. Control: To correct iron deficiency, apply either ferrous sulphate, ferrous ammonium sulphate, or a chelated iron source to the lawn following label directions when first symptoms appear. Chelates are more expensive but will last longer than the other products, which will need to be applied more often. Usually two to four ounces of product are applied per 1,000 square feet. Mix the product with enough water to apply one to three gallons of water per 1,000 square feet of lawn area. Spray the lawn in the morning letting the spray dry all day long. Water the lawn before mowing. Excess iron spray will be stored in the soil and/or taken up by the turfgrass. Be careful not to stain concrete areas with the iron spray. Within a few days the turf should start greening up. Question: I have two things growing on my lawn. One is a black material that feels greasy when I touch it. It is on the ground and also on the blades of grass. The other material is orange-white in color and is moist to the touch, but dries out and is chalky the next day. Any ideas of what these things are? Answer: Did you change your oil over your lawn? If not then the black substance is a slime mold that is dormant in the soil until large amounts of moisture fall on the ground. The environmental conditions are then right for this organism to reproduce and migrate. The other material is a spore mat of a fungus that is in the soil. Again when environmental conditions are right the fungal organism, which lives in the soil, will send up a reproductive structure to spread spores there by reproducing. Control: There is nothing that needs to be done to control these organisms. They were in the soil all along and have just put up reproductive structures. As the ground and air dry out they will disappear only to reappear when the environmental conditions are right. Back to Top
Question: I have elm trees that have beetles that become quite a pest. They eat the leaves. How can I get rid of them? Answer: A sure way to get rid of elm leaf beetles is to cut down your tree(s) and those of your neighbor's! The larva of the beetles are eating the leaves so you must get rid of them. You can spray Bacillus thuringiensis or B.T., the San Diego strain. This product is sold under several trade names and is an organic insecticide that kills insect larva only and is not harmful to other insects or animals. B.T. is a natural occurring soil bacteria that must be sprayed on the leaves and the treated leaves eaten by the larva. B.T. is washed off by rain and must be reapplied. Another solution is to spray a 2 foot band of Sevin insecticide around the tree trunk 6 to 8 feet above the ground. The elm leaf beetle larva travel down the tree trunk to pupate on the lower trunk or near the soil line. Crossing the Sevin strip will kill the larva and over time reduce the insect population according to University of California entomologists. This treatment also will not destroy adults so if there are a lot of elm trees in you neighborhood other elm leaf beetles will fly to your trees and lay eggs. However, these treatments can significantly reduce larval populations and damage to tree leaves. Question: My ash, plum and pomegranate leaf margins are turning brown and drying up. The leaves are yellowish in color with some green remaining between the veins. I have been watering the trees using a well. They are planted in my lawn. I used "Weed and Feed" on the lawn this spring and again during the summer. The trees are just looking sick and I am feeling like the trees. Answer: The trees are showing the signs of herbicide damage. "Weed and Feed" products contain fertilizer and 2,4-D herbicide. Inert particles like clay are coated with the herbicide which releases into the soil when watered. The herbicide 2,4-D will kill many broadleaf weeds in the lawn. However, the herbicide also can damage or kill other broadleaf plants. These trees are showing symptoms but did not receive a large enough dose to kill them. The herbicide reached the shallow rooted trees, was absorbed and you see the symptoms in the leaves. Control: Do not apply 2,4-D type herbicides, (as a spray or in a "Weed and Feed" product), where desired broadleaf plants will absorb them through the roots or leaves. Many broadleaves like roses and grapes are very sensitive to 2,4-D type herbicides. The trees will most likely not show symptoms in the spring. For now the leaves will have to drop so that the trees will not look sick. Just a note on the herbicide 2,4-Dichlorophenoxyacetic acid, (the chemical name), or 2,4-D for short and related compounds. This herbicide comes in several different formulations. If it is to be used around plants that are susceptible, i.e. broadleaf plants, use an amine formulation. It is less volatile than an ester formulation. You must read the label and find the chemical name. If amine or ester appears in the chemical name you will know the type of formulation. Question: I have a number of cottonwood trees, (Populus fremontii), that are growing around the edge of our pond. The younger trees that I planted over the past two years are doing fine. The trees that are older, with trunk diameters of 18 to 24 inches have been dying or dead limbs that appeared this summer. We saw some black beetles under the bark in channels carved out of the wood. What are these and what can we do to save these trees? Answer: After seeing samples of the branches it was determined that damage was caused by a large larval stage of the carpenterworm moth, Prionoxystus robiniae (Peck). The black beetles you saw were secondary pests and not causing the damage. This insect attacks weak trees. Your trees were weakened by three spring frosts that defoliated the trees. This stress allowed the hatching insect larvae to enter the trees. This wood- boring insect takes one or two years to complete its life cycle in warm areas but in cooler areas as long as four years. The eggs are laid shortly after the moths emerge in the spring and continues for about a month. The female can lay 300 to 600 eggs in a sticky mass on host branches or trunk. The larvae hatch and bore into the sapwood where it remains most of the larval stage, going through eight to 31 instar stages. As they mature they extend their tunnels into the heartwood. As the larvae bore they produce large amounts of frass, (droppings), and sawdust. In fact the frass looks like excelsior from cooler pads. This clings in mass to the external bark. Tunnels maybe up to 18 mm, ( 3/4") in width. This boring can be disastrous to host trees by killing limbs which are subject to wind breakage, also ruining the wood for saw-log purposes. Host trees include elm, ash , birch, black locust, oak, cottonwood, maple, willow, apricot, pear and an occasional ornamental shrub. The carpenterworm is distributed all over the United States and all bordering Canadian Provinces. Control: Remove all dead or dying limbs and burn them to kill the larvae. Make sure that the trees are receiving adequate water and nutrients, because the best defense is a healthy tree. Applying a small amount, (1/16 to 1/8 pound per inch of trunk diameter) of nitrogen fertilizer will help strengthen the tree this fall. Too much will invigorate the tree that is preparing for winter dormancy. This next spring apply four times the fall amount in two or three applications. Place fertilizer around the drip line and water in. Insecticides applied in the spring might help destroy other eggs that will be laid, but will do little to destroy the larvae that are feeding underneath the protective bark. Systemic insecticides are of little worth with such large trees. Question: An Arizona oak tree that is growing in the middle of my patio has dead branches under the living branches and its leaves that are falling. The tree is quite large with a trunk diameter of close to three feet. Natural rainfall is the only water it receives. The patio was build two years ago. Why is this happening? Don't oaks stay green year around? Answer: The oak tree is a very large and old specimen. An oak that has a diameter of nearly three feet must be at least 100 to 150 years old. The dead branches are those that are under the living ones. When new growth occurs older branches can be shaded out and not produce leaves; they have served their function and die. Prune out the dead branches to make the tree more sightly. Leaves of evergreen do not live forever but their don't fall all at once. During certain times of the year it is natural for some evergreen leaves to fall. By placing a patio around the tree perhaps some of the roots do not have the access they once did to rainfall. However, it must be remembered that mature trees normally have actively feeding roots only 40 to 60% of the distance in from the drip line towards the trunk. Remember that trees do not live forever. Only some species will out live humans. Question: I have some Eldarica pines that have funny curling needles. They occur on last years needles but form nearly complete circles. What is happening to these needle and will it affect the future growth of the trees? Answer: The damage to the needles is caused by eriophyid mites. There are probably more unknown and undescribed species of these mites than any other group of arthropods. They are very small and are measured in micrometers or microns. They are worm-like and slow moving. Injury in conifer species is expressed by chlorotic needles, and/or dwarf, distorted, or short needles. Also by rosette bud/needle clusters similar to a witches broom, by galls, and by partial defoliation of old as well as the current season's needles. Eriophyid mites are found in or on the buds and foliage of all North American conifer species. Many other plants are affected by these animals including deciduous trees and shrub. Control: There are no control measures that are recommended for
eriophyid mites on conifers. The effects of the damage will not cause the plants
to die, however, they can cause unusual growth. Question: I have a pine tree that has masses of sap that look like large bubbles or balloons. These occur on small branches near the tips. Some of the needles are dead or dying. What is causing this and what can I do to prevent it? Answer: The mass of sap you see is the result of an insect larvae that is living inside of the blister-like bubble. If you "burst the bubble" you will find a pitch twig moth larvae. There are several species of pitch moths, however the one you have is most likely Petrova comstockiana (Fernald). Eggs are laid singly on the bark of limbs, the hatching larvae tunnel into the bark and cambium region and establish feeding sites. The pine tree exudes pitch and the larvae then uses the pitch to construct a "home" which includes frass or insect droppings. A mature larva is about 25 millimeters long and has a brownish head and light yellow body. Pupation takes place within the pitch mass and adults emerge during the summer months. In some species about half the population requires one year to complete a life cycle; the other half requires 2 years. In the case of this larvae it will feed on one site for one year then move to a new site, usually a branch crotch, and feeds for another year. Thus two years are required for full development from the feeding stage to a pupal stage. Adult moths emerge only in the summer. Control: Normally there is no need to control these insects. Populations in our area rarely if ever reach economically damaging proportions. If they are really a problem then killing the larvae by pruning out and burning the "bubbles"; or open the bubble and impale the larvae on a wire will decrease the population. Source: Insects That Feed on Trees and Shrubs, 2nd Edition. Warren T. Johnson and Howard H. Lyon. 1991. Page 72. Question: What are these fussy brown spots about 1/8th to 1/4 inch in diameter on the underside of oak leaves? The affected oak trees were planted last spring. Answer: At first it looked like an egg mass of a lepidoptera, that is the moth and butterfly family. After further examination of the sample leaf it was determined to be a gall of the woolly leaf gall caused by cynipid wasp. Other gall forming insect are other wasps, aphids, psyllids or other insect. Most galls are formed as a reaction of the plant to larval feeding or adult egg laying. Most of the time the gall is formed from the reaction of chemicals that the insect secretes which produces mutation of plant cells. This abnormal tissue many times provides cover over the newly laid or hatched eggs. Also many times the inside gall tissue is a food source for newly hatched insects. Question: We live up in the mountains and have many oaks on our property. We have noticed brown growths near the end of branches that looks as if someone had thrown cow manure into the trees and it stuck! Also, we have some round "balls" hanging from the oak trees as well as some growths that are near the end of young twigs that look to be impaled on the twigs. What are these and where do they come from? Answer: Wherever oaks occur, they are attacked by a small group of
insects called galls makers. These insects cause deformities of plant tissue.
The majority of gall making insects that attack oaks are wasps. Galls are
produced by powerful plant growth-regulating chemicals or other stimuli produced
by the insect that react with plant hormones. Some stimuli are feeding or egg
laying. The inner walls of the galls are rich in protein and thus provide the
larvae living in the gall a concentrated food source. The larvae are somewhat
protected from predators while they are in the galls. Galls come in several
shapes and sizes. They can be globular, dish-shaped or look like thorny, spiny
balls. Galls are specific as to the kind of oak they occur on. For example,
those found on the black oak group do not occur on the white oak group. Many
galls exhibit a characteristic gall alternation of generations. That is that the
offspring of a gall wasp may produce galls that are completely different from
those produced by their parents, but identical with those by their grandparents.
Also, the site of the galls usually will be produced on a different part of the
tree than those of their parents. It is reported that 717 species of gall wasp
are found in North America. That number is decreasing as biologists unravel the
mystery of alternating generations pairs and identify single species. Question: I have some juniper trees whose tips are turning brown. The trees were planted over 20 years ago and they receive enough water. When the branches are moving a yellow powder falls out of the "infected" area. What is causing the browning of the tips. Is it an insect or a fungus of some kind? Answer: After examining a sample of the plant it was determined to have normal growth. The small brown tips are the developing male portion of the trees and when mature will produce pollen. The yellow power that falls off the plant when disturbed is indeed pollen. Question: The cottonwood in our back yard has several limbs that are dying in the center of the tree. It is growing in a fescue lawn. What is causing this to happen? Answer: Cottonwood trees are native to rivers, streams and washes in Arizona. They require a lot of water. You need to water the lawn and then deep soak for the cottonwood tree. If you water shade trees with only the 1 to 2 inches of week per water required by the lawn you will not supply the 3 to 6 inches of water per week that large trees will need. This is because lawn roots are primarily in the first foot of soil. The majority of tree and shrub roots will be in the top two to three feet of soil. During the hot summer weather trees will extract large amounts of water from the soil each day. Shallow watered tree roots will tend to be closer to the surface of the ground. However, the genetics of the tree has a lot to do with the depth of rooting. I have known of several cases where the tree roots where growing up to the soil surface and the owners cut the roots out so they would not have to run over them with the lawn mower. By doing this you sever the roots that uptake nutrients and water to specific limbs of the tree causing them to die. Question: I have several trees, shrubs and bushes that have leaves that are turning yellow but the veins remain green. I water them every other day and feel that they are receiving enough water. What can I do to correct this problem? Answer: The leaf yellowing is called iron chlorosis and is caused by insufficent iron in the plant leaves. If you look closely you will see that the older leaves are not effected. Iron is necessary in the formation of chlorophyll, the green pigment of plant leaves and stems. Our soils are alkaline, meaning that they have pH's above 7.0. As soil pH increases above 7 iron forms other molecular complexes which are not taken up by plants. Water logged soils or anarobic conditions can cause iron to be unavailable. Control: Decrease the amount of water given plants, checking the soil to see if watering is necessary. Lowering soil pH will make iron more available. Changing soil pH is a long term proposition but can be accomplished by adding acidifing materials such as soil sulfur and/or gypsum. Iron can be applied to the soil or the leaves to help correct this problem. Iron applied to the soil is slower acting but is longer lasting than iron sprayed on the foliage. There are several dry products that can be soil applied; these include "Ironite", iron sulfate and other forms of iron. These products are poured into holes that are about poked into the soil one to one and a half feet deep, placed around the drip line of the affected plant and serves as a reservoir of available iron. Foliar applied irons are usually liquids and can also come in chelated forms. Chelates are "chemical jaws" which protect the iron from becoming bound up with other chemicals before it is inside the plant. Once near or inside the plant the chelating agent is dissolved and the chelated chemical is available. Chelates can be applied to the soil also but only Sequestrene 138, (6% iron), will work well in our alkaline soils. It is red in color as a powder and when added to water has the color of blood and is expensive as blood! The Sequestrene 330, (10% iron), is yellow in color and is applied to the foliage only. It should only be soil applied to acid soil, if not it will become bound up and not available to the plant. Look at the product color to know which chelated iron is being used and how to properly apply it. Always read and understand the label before using chemicals. Question: My mesquite tree has mistletoe in it. Is there any way to rid my trees of this growth? Answer: There are several genera and species of mistletoe. In Arizona we have 5 species of Phoradendron (leafy mistletoes) and 3 species of Arceuthobium. The latter, called dwarf mistletoe, infests only conifers. Leafy mistletoes are considered as "hemi-parasites", which means that they produce some or all of their own energy through photosynthesis but depend on the host for water and minerals. Mistletoes elicit a disease response from most hosts and are considered pathogens. However, mistletoes seldom kill healthy hosts except dwarf mistletoe, which can cause severe damage in coniferous forests. Severely infested trees usually have been subjected to other stresses that increased their susceptibility such as drought, flooding, soil compaction, nutrient deficiencies, etc. The "root" of a leafy mistletoe is directly connected to the host's xylem (that part of the plant's plumbing that conducts water and minerals from the roots to the leaves). The "root" of a dwarf mistletoe is connected to the host's phloem as well as the xylem. The phloem conducts sugars and other products of photosynthesis from the leaves to other parts of the plant. So the dwarf mistletoe is highly parasitic, depending on the host, for photosynthate as well as water and minerals. Leafy mistletoes can occur on several hundred host species. Mistletoe creates a drain on host resources that reduce growth, decreases vigor, and increases susceptibility to other diseases and insect pests. Local symptoms can include dieback, formation of witches' broom, and weakened branches. Dwarf mistletoe, in particular, can cause spiketop, where the entire host crown dies and also causes witches' broom which increases the diversion of water, minerals, and nutrients to the site of infestation. Control: Removal of the branch below the mistletoe remains an economical and fairly efficient method of mistletoe "control". However, control by pruning requires diligence. Birds eat mistletoe berries and spread the seed which is unaffected by the digestive tract. So any fruiting mistletoe that survives pruning is a source for reinfestation. Chemical treatment has not been effective to date. In one study 2,4-D was injected in infected eucalyptus trees. The chemical killed 70% to 100% of the mistletoes, but partially defoliated all trees and killed 5% of them. Recent research efforts have focused on interrupting fruit set with hormone sprays combined with pruning. Resistant cultivars and biological control remain as possible long term solutions. Wrapping the mistletoe and infected branch with black plastic to block light and increasing heat has proven somewhat effective. The plastic must remain around the branch for several months. Source: Paine & Harrison. 1992. HortTechnology 2:34-330. Question: My mesquite trees have brown round bumps on many of the limbs. In fact some of the branches have ooze dripping from them. Is this scale? Answer: Yes the problem is scale, soft brown scale in fact. Scale are a "super family" of over 200 insects that feed on plant sap while females protect themselves with a soft or hard "shell" body covering. Males can be winged. Scale produce young by eggs or by bearing live young. The young, called crawlers, may crawl out from under mother's covering and move to another location, usually close by, and then set up "housekeeping". One to five generations will be produced each year depending on the species and environmental conditions. Scale are protected by the covering they make for themselves and it is very hard to penetrate with pesticides. Control: Physical removal by spraying a hard stream of water may work, however many times they are stuck on the plant very tightly. Even rubbing off the scale with a stiff brush can be effective. Using systemic insecticides can help control scaled but many times does not work very well. Suffocating or penetrating their "shell" are methods also used to kill this pest. Dormant oil sprays are used when plant leaves are no longer than a half inch in early spring. If used later leaf damage may occur. Rubbing alcohol applied to scale will penetrate their waxy shell covering and kill them. Use 70% isopropyl (rubbing) alcohol, mixing 1 to 2 cups of alcohol per quart of water. Since alcohol can damage some plants first test spray on a small area. Wait for a day or two to see if damage occurred, if not it is safe to spray. You can mix insecticidal soap up according to the label directions but substitute rubbing alcohol for half of the water. A recipe a that has proven effective in the past for scale control and other insects is made by mixing one cup cooking oil plus 1 Tablespoon of dish detergent (non-citrus). Mix one to two teaspoons of this solution with one cup of water. Spray mixture on the infected plant until it drips off. It is best to spray a few leaves and then check for leaf burn the next day before spraying the entire plant. With many of these treatments the scale will not drop off of the plant but will remain attached even though they are dead. Pry some off several days after treatment to determine if the scale are dead. If not treat again. Questions: I have several 12 year old Arizona cypress trees with needles that are turning brown. The middle to center of the limbs on the lower branches are affected. What disease is causing this? What can I do about it? Answer: As evergreen trees get older the leaves, called needles or scales, on older branches, (those that are close to the tree trunk or base of the tree), will naturally brown and fall off. These leaves are old having served the tree well but have become shaded out and are not contributing to the tree's growth. During normal winters adequate moisture falls. This winter however was unusually dry. Because of little or no moisture supplemental water was necessary. Several people have called with questions about browning evergreens. Usually people will state that they did not water their trees last winter. Evergreens need about one third the of water during the winter compared to the rest of the year. Therefore, water the trees and watch for new growth. The tips of the branches should be green and healthy because that is where shoot growth takes place. Also, water at the tree drip line and out from that point. Feeder roots are located usually out from the drip line not next to the tree trunk. I trees are planted through plastic that has crushed granite or gravel on top, take a pitch-fork and poke holes through the plastic to allow rain fall into the soil. Question: I have several Arizona Cypress trees that are dying. There are holes in the trunks and the tips are breaking off. What is happening to my tree? Answer: The problems observed on your tree are two different insects. Both are aggressive pests of stressed cypress and junipers on Arizona. The first is Western Cedar Borer. This borer will attack and seriously injure or kill trees. It seems to prefer older, large trees. Adults are bright emerald with serial dark areas on the wing covers. Flatheaded larvae bore from the branches into the main trunk where they feed on the heartwood for several years. The second insect is the Juniper Twig Pruner. It causes dieback on the tips of tree branches. The insect is a small long-nosed beetle. The adult has a reddish-orange head and brownish to black body. Eggs are laid on the branches, often near an intersection of twigs, one to two feet from the branch tip. Larvae are small, white, cylindrical, legless grubs that kill the twigs by boring though the centers. The life cycle may take as long as two years to complete. Control: No practical controls or preventive measures have been developed for Western Cedar Borer or Juniper Twig Pruner. The Juniper Twig Pruner damage can be unsightly when populations are high but this pest rarely seriously injures trees. However, the Western Cedar Borer will kill trees. Question: I have a 'Globe Willow' that has a dark-colored sap running down the bark. I seem to be coming from under the wood near the crotch of the tree. What is the cause of this? I see some insects in this sap. Is there a bore causing the damage? The dark sap is dripping on my patio and discoloring the flagstones. What can I do? Answer: Your tree is suffering from a disorder called slime flux or wet wood. These two diseases are thought to be bacterial infections, however these diseases are poorly understood. The water soaked, discolored appearance with constant bleeding of the sap at or below the branch crotches and trunk are the visual symptoms of this disease. Liquid may seep out of cracks or wounds and run down the bark. The liquid contains microorganisms that will cause the liquid to ferment and become dark in color, sticky and smelly and some insects may feed on it. Pressure can build up under the bark from fermentation and cause splitting and cracking. Normally the disease is not observed in young trees probably because of rapid growth which makes invasion of bacteria and fungi rare. Generally trees are at least 5 years old and have developed heartwood become infected. Wilting and die back of branches may occur. Younger trees may have leaves that yellow, wilt or curl, turn colors and then drop early. Susceptible trees grown in Arizona include: ash, (Fraxinus species), elms (Ulmus species), poplars (Populus species), willows (Salix species), mulberry (Morus species), and mesquite; common, honey and chilean (Prosopis species). Control: Slime flux infection can aggravate wounds and cause death of bark cambium. This disease may need to be controlled in large specimen trees. Holes may be drilled to relieve pressure under the bark. Drill a 1/4 or 1/2 inch hole at an upward angle below the bleeding and insert a plastic tube snugly and permanently into the first inch or two of the hole. This reduces the internal pressure and facilitates drainage of the fermented toxic material. Remove any dead or weak branches. Fertilize and water to keep the tree in a vigorous state. For the stains on your flagstone place a piece of cardboard or plastic to catch the dark liquid. If the stone is stained perhaps bleaching would help. Question: I have a young spruce tree that is drying up on one side. The needles are falling off and part of the tree is bare. The tree is watered well. The tree is planted three feet from the northwest side of the house. What is the problem? Answer: The tree is probably infected with spider mites. This can be determined by placing a white piece of paper under a branch while giving the branch a quick tap. Spider mites will be dislodged, fall on the paper and look like little speck running around. These animals are not insects but arachnids, members of the spider family. With a magnifying glass you can see that these tiny creatures have two body parts: a head and a abdomen, and eight legs. There are numerous species of mites, both harmful and beneficial. Spider mites thrive in hot, dry weather. Trees planted to close to a house will try and push the house over! Also the afternoon sun reflects heat off of the house on to the tree and provides a perfect environment for mites. Control: If proper cultural practices are used predacious mites normally control harmful mites. If mites become a problem washing them off with a hard stream of water can help destroy small infestations. Dormant oil sprays applied during early spring also help keep mites in check. Dusting sulfur is labeled for mites and is an organic treatment. Care must be used when using sulfur during high temperatures because burning of plant tissue may occur. Chemical miticide are available to control sever infestations. Registered products include Kelthane (dicifol), and Omite (propargite). Always follow the label instructions when using any pesticide. Back to Top
Question: When should I prune my trees, shrubs, fruit trees, berries, grapes, and roses? Answer: Pruning is a dwarfing, stimulating and stressful event. It's best to start most pruning January or February. However, diseased or dead limbs and root suckers can be removed at any time. In the fall plants are slowing down and entering a dormant period. The dormant period is a physiological stage where buds cannot be forced to grow even under ideal conditions. Trees and shrubs are moving compounds from the leaves and branches and storing carbohydrates in the trunks and roots. Pruning during fall and winter may stimulated buds that are going dormant to begin growing using energy and other resources that are normally stored to survive winter. Next spring's growth takes a lot of energy and if used up in the fall and winter because of pruning stimulation and can cause plants to become stressed and even die if winter conditions are severe. All of this growth needs to occur in the spring before photosynthesis can begin anew in deciduous plants. Even evergreens' growing activity in the winter slows and in some cases stops. Stimulating new growth is just opposite of what the plant needs to have happen to survive the winter season. This is harmful when plants should be going "to sleep." A plant that has been pruned in late fall can be damaged or killed when it starts growing and a freeze occurs. Pruning of pine, juniper, cedar, fir, and spruce tree and shrubs should be done during the spring. Pruning is a stressful event for nearly all plants. The mentioned conifers are not growing much if any during the winter season and will have growth start in the spring. Waiting until spring to prune or trim these plants will afford them the opportunity to heal properly because of the strength they will have during the spring push of growth. Pruning of fruit trees should be done when trees are dormant, after rest is completed in the winter. Generally rest requirements are obtained after Christmas. Pruning can be started in January and continue through bloom in the spring. Fruit trees can be pruned until flower pedals fall. For stone fruits; i.e. apricots, almonds, cherries, peaches, plums and nectarines and for pome fruits; i.e. apples, pears and quince pruning can continue until bloom is completed. Small fruits; i.e. blackberries, grapes, raspberries, currants and gooseberries are best pruned during the dormant season. Grapes can be pruned through bloom but have a tendency to "bleed". This is not as detrimental as one might think and it is better to prune grapes a little late than let them grow in to a knurled mass! Blackberries and raspberries bare fruit on one year old canes. The two year old canes need to be removed because they have born fruit and are dead. Thinning out weak canes can also be done through bloom. Currents and gooseberries should be dormant pruned by removing wood that is 3 years old by cutting it back to the base or to a main branch. Roses that bloom several times during the year should be dormant pruned in the late winter or early spring before new growth begins. Roses that bloom only once during the year are pruned after blooming n late spring or summer after flowering. Roses are dormant pruned except in the case of climbing roses which are pruned after flowering. If you have question on a specific plant's pruning requirements contact the Extension Office in Sierra Vista or Willcox or consult a good pruning book like Sunset's Pruning Book.
Question: When my roses bloom they have brown and black petal edges and are deformed. Also the leaves are sticky. Some of the leaves are covered with yellow spots mixed with the green color of the leaves. What is causing these problems and what can I do? Answer: Your roses have two insect problems and a virus. The flower petals are brown or black because of a very small insect called the western flower thrip, Frankliniella occidentalis (Pergande). Adult thrips are about 1/8", (2 mm), in length, usually tan-to-dark brown-bodied, with four feather like wings. The young or nymphs are creamy white and wingless and develop into adults in about two weeks. The adults enter a rose bud and lay eggs inside the immature flower. The eggs hatch and the resulting nymphs and adults injure the plant by rasping the bud, flower and leaf tissue of host plants and then suck the exuding sap. This causes petal tissue to die and results in brown or black petal edges. Thrips also affect other flower, fruit and vegetable plants. These include apples and peaches which result in surface damage to the fruit. Onions, snap beans, chrysanthemums, gladiolus and iris are also damaged by other thrips species. There has been many more thrips the last couple of years because of the above normal rainfall which has provided abundant wildflower and weed crops for the thrips to live on and thus increased populations. The other insect problem is aphids. These small insects are yellow to green in color and suck sap from plants that they infect. The "sugars" which they do not metabolize are excreted and fall onto the leaves of the plant. This is the sticky, shiney substance that you see. Sometimes ants and flies will "milk" aphids for this exudate and feed on it. So if ants are spotted on plants there is a good chance that aphids are present. The yellow marks mixed with the green color of the leaves is a virus or a complex of several viruses. The spotted yellow-green leaf color is known as mottling and is very symptimatic of viruses. These viruses generally do not kill the plant but can weaken it. Control: Several insects are predators of thrips and aphids. These include ladybird beetles and their larva, minute pirate bug and lacewings. Thrips have alternate hosts of weeds and wildflowers. By controlling host plants thrip populations will be lowered. Because thrips do damage inside the rose buds a systemic insecticide should be used. There are several products on the market which control thrips and aphids systemically. Sometimes disystox, a systemic insecticide, is included in rose fertilizer. Always follow label directions when applying pesticides. To reduce the problems of viruses in plants purchase virus-indexed or certified virus free plants. Virus infected plants can be a source of infection that can be transmit to healthy plants by aphids or other insects. Therefore, control the aphids and other insects vectors to control the spread of virus diseases. Source: Insect Pests of Farm, Garden and Orchard. 7th Ed. R. H. Davidson and W. F. Lyon. pp. 305-6, 311-12. Question: The leaves of my roses are drying up. The leaves have a white-grayish fuzzy material coating them. What is this and what can I do? Answer: Powdery mildew is affecting roses. Powdery mildews are common, widespread, and on many crop and ornamental plants. The total loss by these organisms each year probably surpass the losses caused by any other single type of plant disease. There are many species of powdery mildew. Your apple tree was probably infected by Podosphoera leucotricha and your roses by Spaerotheca pannosa. These fungi are common and cause serious problems in cool and warm humid areas, but are even more of a problem in warm dry climates like Arizona. Powdery mildew spores (fungal "seeds"), can be released, germinate, and cause infection when the relative humidity in the air is fairly high, but there is no film of water on plant surface. This spring, with abnormally high rainfall, has favored the growth and spread of powdery mildew. Once infection has begun the fungus spreads on plant surfaces regardless of the moisture conditions in the atmosphere. These organisms send haustoria (feeding organs), into the epidermal cells of plants to obtain nutrients. Powdery mildews are obligate parasites; meaning they cannot be cultured on artificially growing media in the laboratory but must grow on the their specific hosts. Powdery mildew seldom if ever kills its host but utilize their nutrients, reduce photosynthesis, increase respiration and transpiration, impairs growth, and can reduce yields as much as 20-40 percent. Control: When planting roses or other susceptible plants place them in location with good sunlight and air flow, i.e. not up against the house. Prune plants properly to open them up to ensure air flow through the plant. A rose or euonymus planted on the shady north side of a house will surely have powdery mildew problems. Many new rose varieties have disease resistance to powdery mildew. This resistance will help, but may not completely eliminate the need for chemical control. Chemical controls include spraying or dusting sulfur. Care must be taken not to apply sulfur on hot days because plant tissue can be burned. Other chemical controls include benomyl (Benlate), triadimefon (Bayleton) and triforine (Funginex). Source: Plant Pathology, George N. Agrios. Third Edition, 1988, pp. 337-342. Back to Top
Question: Are there any garden vegetables that can be planted for a fall harvest in Cochise County? Answer: Yes! Many of the cool season crops, those that can withstand freezing temperatures, do very well in Cochise County in the fall. In fact, the fall in Cochise County is better generally than the spring to raise cool season crops. These vegetables include the [brassica] family - broccoli, cauliflower, kale and cabbage among others. Also, spinach, beets, peas, radishes, lettuces, mustard greens, and other greens may be planted. The onion family, which includes garlic, does well when planted in the fall and then over-wintered and harvested in early spring. Question: I have several cucumber, pumpkin, and squash plants that have discolored leaves and distorted leaves. I see no insect damage and have sprayed for powdery mildew. The plants have adequate nutrition and are watered regularly. What's wrong with my plants? Answer: Your curcurbits, (squash and melon family), have been infected with a virus. There are several different viruses that infect this family of plants. They include: cucumber mosaic virus (CVM), squash leaf curl virus (SLCV), squash mosaic virus (SQMV), watermelon mosaic virus (WMV) and zucchini yellow mosaic virus (ZYMV). Each of these pathogens usually have several strains. Sometimes an infected plant may have more than one virus causing the symptoms. Therefore, it makes an exact diagnosis difficult with out laboratory work. Plants will have mottled leaves, that is patches of green and yellow, often in varying hues mixed in the leaf. Whole plants and leaves are usually smaller than normal and many times deformed and fragmented. Cucumber, melon and squash fruit are also small, stunted and colored unusually. The fruits at times will have warts and be bumpy. Viruses can not survive outside of living organisms. They may be contained in the seed when planted, which occurs with SQMV. Insects serve as vectors, (transmittance agents), for many viruses. Sucking insects like aphids and white flies and chewing insects such as cucumber beetles and grasshoppers transmit virus particles from infected plants to healthy ones. Control: Some virus resistant varieties are available; their use is advisable. Control of host plants like weeds serve as stores of viruses as well as infected crop plants. Destroy these plants as soon as symptoms appear. Control insects which transmit viruses from one plant to another. I know of no chemical or natural cures for viruses in plants. The plant many times will live in a weakened state much like what happens to humans when we get a viral flu or cold. Question: I have strawberry, raspberry and grapes that were growing well but now have leaves that are drying up around the edges and in the middle of the leaves. I water every day for five to ten minutes with overhead sprinklers that are on a timer clock. Do these plants have a disease? Answer: Your plants are not getting enough water for two reasons. The first is that water volume and watering duration are not adequate. The second is that as you water salts in the water are added to the soil in addition to natural salts that are native to our desert soils. These salts, in part, are sodium, carbonates, calcium, chlorine and perhaps some heavy metals. To correct the problem start watering every other day for a half hour then check the water penetration depth using a soil probe or long screwdriver. If they go in an inch or two in the ground then you need to water. If it goes in a foot or two don't water. Once a month or so a deep watering is needed to leach out salts causing them to past the root zone. The drying of the leaf edges is cause by the plant taking up salts through the root system which are then conducted up to the leaves. The leaf cells "pump" out water into the "saltier" intercellular spaces so that equilibrium is reached between salts within and without of the cell. This removal of water from leaf cells causes the drying that you see. Question: Why don't I have any summer squash being produced? There were some fruits early on in the season but now there is just vines and flowers growing. Also my tomatoes are not producing and some that have had fruit are cracked. What can I do? Answer: With hot weather pollen of some plants becomes less viable and does not pollinate therefore fruit do not form. When the hot weather stops then fruit will set. This is also true for tomatoes, bell peppers, chili peppers and some members of the squash family. Tomatoes will crack from hot weather also and irregular watering. The biggest factor causing tomatoes to crack is the variety genetics. If a variety description list the tomato as crack resistant it will probably not crack. A crack resist tomato variety is "Mountain Pride". Question: My tomatoes have small water-soaked areas that at first appear to be bruises, then turns into brown sunken leathery areas always at on the blossom end of the fruit. Some of the sunken areas turn black. These diseased fruits usually ripen before the non-infected fruit. What disease do my tomatoes have? Answer: This disease, call blossom-end rot, is caused by a localized deficiency of calcium in the fruits. Calcium is required in large quantities by growing cells like those in the blossom-end. When this rapidly growing tissue is deprived of the calcium needed for growth, especially cell-wall construction, tissues break down resulting in blackened, dry sunken spots or areas on at the blossom-end of the fruit. Water stress usually creates this disorder because inconsistent watering will not allow the plant to translocate sufficient calcium. Also high levels of nitrogen can cause vigorous growth early in the season which with water stress can compound the problem. Blossom-end rot is also seen in chili and bell peppers and members of the squash and melon family. Control: It is important to regulate soil moisture and maintain that moisture at a relatively constant level where possible. Plenty of organic matter in the soil and mulching plants will help maintain consistent soil moisture. Also avoid high applications of nitrogen to the plants. Some varieties of tomatoes are less susceptible to blossom-end rot. These include Early Girl, Floradel, Floradade, Tropic and Jet Star. It has been demonstrated that foliar sprays of calcium chloride, (1 lb./25 gallons of water), or calcium nitrate, (2 lbs./25 gallons of water), can help reduce this problem. Applications must be made before calcium levels fall below critical levels and must be applied weekly for 3 to 4 weeks. Source: Vegetable Diseases and Their Control. A. F. Sherf and A. A. MacNab. 1986. pp. 689-691. John Wiley and Sons, New York. Question: My tomatoes have cracks around the stem end and black sunken tissue on the blossom end. What is wrong? Answer: Cracking around the stem is caused by high temperatures and watering practices. However, the cracking is genetic in that there are varieties that do not crack. The "Mountain" series, including "Mountain Pride" and "Mountain Delight", from North Carolina do not crack. The other problem is called blossom end rot. It is a physiological condition that arises because of varying moisture in the soil. The plant cannot transport enough calcium to meet the demand in forming cell walls even though there is plenty in the soil. Most nutrients are carried in water to uptake sites on the root hairs. Sometimes a secondary fungus like sooty mold will colonize the tissue, causing a black fungal growth. Other plants like squash, pepper, chile and melons also can have blossom end rot. Control: Water consistently and deeper and apply mulch to keep soil moisture consistent. Early fruit have more blossom end rot problems that fruit produced later, so be patient. The fruit is still edible just cut out the bad parts. Question: Why are the melons and winter squash that I planted in May looking so poor? Some of the skin of the fruits are soft and yellowish while others very brown and the skin is hard. What should I do to grow good melons and winter squash? Answer: You have sunburned fruit. It is to late to apply sun-tanning lotion! I have found that it is best to plant melons, pumpkins, and winter squash after the first of July. The reason is that normally we will have some cloud cover and rain while the really hot weather of May and June is subsiding. Soil temperatures are warm enough so that seeds germinate rapidly. If you plant just after the last spring frost the plants will grow normally. However, the fruits will be produced to early and become sunburned because of the heat and poor leave cover, which shades the fruit, during the month of June when compared to plants sown in July. We have a long enough growing season to mature these crops in September and October. Our normal first fall frost in Cochise County is in late October. Try planting melons, pumpkins, and winter squash now and you will have better results, I guarantee!
Question: There are two weeds that grow on my property that produce burrs. One is clover like and the other is a grass. They stick to clothing, blankets and animal flesh including my own! What are they? I spray them with herbicide but they reappear. How can I control them? Answer: The two plants that are producing burrs in your yard are bur clover, Medicago hispida Gaertn., and field sandbur, Cenchrus pauciflorus Benth., which is a grass. Both of these plants are annuals and sometimes short-lived perennials reproducing from seeds. Bur clover is a low trailing plant found in lawns, gardens and along roadways and waste areas. Plants stem weakly, branching from the base and radiating out from a taproot one quarter to two feet long. Leaves are composed of three lobed clover-like leaflets with toothed edges and indented tips. Where the leaf joins the stem there is a pair of small leaf-like structures. Yellow flowers are produced during early spring and late fall. Seeds are found in spiny pods. The pods are straw colored or brown when mature and contain several kidney shaped seeds which are yellowish or tan colored. Bur clover should not be confused with another weed of the same genus called black medic, Medicago lupulina L., which is very similar but has hair, not spines on the seed pods. Both are natives of eastern Europe and Asia and are cousins of alfalfa. Field sandbur, Cenchrus echinatus L., is a warm season grass found in dry, sandy, cultivated soils in lawns, roadsides, washes and waste places. Plants are from eight inches to three feet tall with shallow roots which spreads horizontally forming mats. Leaf blades are flat, but can be twisted or folded and are two to five inches long. Reproduction is by seed or by prostrate stems that root. Burs grow in spikes one to three inches long and bear 10 to 30 burs each that are a shiny straw yellow that contain two seeds. Each plant can produce up to 1,000 seed. Control: These annual weeds arising primarily from seeds. Cultivation of
young and/or mulching before seeds germinate can control these plants. On
non-crop land soil solarization, using black plastic, can kill weed seed.
Control with herbicides like Roundup or 2,4-D is best accomplished on young
plants. Herbicides or cultivation of mature plants will not control these weeds
in the long run if seeds are allowed to mature. If seeds are allowed to develop
then chemical controls must applied before seeds germinate. Bur clover
germinates during the cool weather of early spring or fall. Sand bur germinates
during the warm weather of spring or summer. Herbicides that can be applied
before seeds germinate are Gallery, which controls broadleaf weeds like bur
clover or Surflan would be a second but not as effective choice. Field sand bur
growing among broadleaf plants can be controlled using Poast or Fusilade. On
non-crop land several compounds can be used including Stomp, Bueno or other soil
sterilants. Some of these compounds are only available to pesticide applicators.
As with all pesticides read the label and understand their use. Home | Back to Desert Gardening | Back to Newsletter
|
