|
PESTS OF LANDSCAPE PLANTS [continued]
|
|
SAP FEEDERS
|
|
Hemiptera
Cactus Bug
Cactus bugs are true bugs with sucking mouthparts. They are light
yellow with a dark brown head, with a wide yellow stripe down the
back of their head, and a darker triangle in the middle of the
back. Females attach their eggs to the underside of cactus spines.
Cactus bugs are introduced pests of Opuntia cactus. Their feeding
causes yellowing of the pads and sometimes death of the plant. |
Lacebug |
Lacebugs Lacebugs are flattened insects,
roughly rectangular in shape when viewed from above. They take
their name from the lace-like expansions projecting from the
thorax and front wings. Several species are found in Arizona.
Adult females lay eggs near the leaf veins on the underside of
leaves. Nymphs and adults suck sap from the underside of leaves of
plants such as basswood, sycamore and lantana. They are also
destructive to composites and annual flowers. The feeding damage
looks similar to spider mites, except lacebugs often leave dark
spots of excrement as well as causing yellow stippling. |
Aphid |
Homoptera
Aphids
Aphids vary in color depending on the species and their host.
Numbers can build up quickly because the adults are capable of
producing live offspring without mating. They feed in groups,
often on the growing tips of a plant. Aphids suck the juices from
a plant, and the excess they excrete as a sticky material called
honeydew. A black fungus known as sooty mold often grows in the
honeydew, and if there is enough covering the leaves it may
interfere with photosynthesis. |
Cotton Aphid Nymph |
The arborvitae aphid is a brown species that
infests arborvitae, Italian cypress and false cypress. |
The cotton or melon aphid is dark green
to black in color, and feeds on cotton, oranges, melons, poppy,
chrysanthemum, cucumber, dogwood, begonia, milkweed, spinach,
beets and many others. |
Cotton Aphid Adult |
The oleander aphid is a yellow-orange aphid
with black cornicles found on oleander during the spring and on
desert milkweed at other times. They rarely cause significant
damage to either plant, and may actually be beneficial because
they serve as food for biological control agents. |
|
The rose aphid is a relatively large species
which is either green or pinkish in color. It is commonly found on
the unopened flower buds. |
|
The rusty plum aphid is a rusty brown species
found feeding on plum, corn, grasses and many wild flowers. |
|
Aphids may be washed off with a garden hose, but be
careful when temperatures are high because the water may cause
leaf burn. If aphids persist, try spraying with a solution of up
to two tablespoons of liquid detergent per gallon of water. Test a
small number of leaves first, because some plants will be
sensitive to soaps. |
|
Cochineal Scale
Cochineal scales may be mistaken for mealybugs. The females are
red in color with white waxy plates, which gives them a cottony
appearance. The species in Arizona feeds on Opuntia (prickly pear)
cactus. The insects may be brushed from the cacti, dried and their
red color used as a dye. |
|
Several insect predators control this scale, including
several species of lady beetles, syrphid flies and lacewing
larvae. |
Leafhopper |
Leafhoppers
Leafhoppers are wedge-shaped insects, about 1/8 inch long with
jumping legs. They are capable of strong flight. Some species may
be serious pests. They suck the juices from the plant and excrete
excess fluids in the form of honeydew. As with aphids, this sugary
substance may support the growth of sooty molds. |
Because they are so mobile, leafhoppers may be
difficult to control. Floating row covers may be used to prevent
leafhoppers from damaging gardens. |
Whitefly Adult |
Whiteflies
Adults are less than 1/16 inch long and have a pale yellow body
covered with a white waxy material. The sedentary, scale-like
immatures suck sap from the under side of leaves. The species of
whitefly that is currently the most significant pest becomes
abundant in late summer and early fall. However, other species of
whiteflies are found here, including greenhouse whiteflies, ash
whiteflies and banded-wing whiteflies. These species may be
abundant at different times of the year and require different
control measures. |
Whitefly Immatures |
Control whiteflies by spraying the underside of leaves
with a mixture of one teaspoon to two tablespoons of dish
detergent per gallon of water. Test for toxicity to plants by
starting at the lowest dose and gradually increasing the amount of
dish detergent added. Spray every three to four days or as needed. |
Spider Mites |
Class Arachnida
Spider Mites
Spider mites are tiny creatures, some less than 1/50 of an inch.
Most are so small they can not be seen without the aid of a
microscope. Mites are usually oval or rounded in shape, and may be
yellow, red, greenish, or brownish in color. Spider mites get
their name from the fact that they produce a fine webbing between
leaves, a sign of infestation. They suck sap from leaves and
fruit, which causes yellow spots or ÒstipplingÓ on
the leaves. Their feeding may cause deformations such as twisting
and stunting of leaves, as well. Other types of mites cause galls. |
|
A mix of soap and water may be used to wash plant mites
off leaves, as with whiteflies. Several biological control agents
are also available for the control of spider mites. |
|
TRUNK AND/OR LIMB FEEDERS |
Flatheaded Borer Adult |
Coleoptera
Flatheaded Borers
Adult flatheaded borers are 1/2 to 3/4 inch long, often
olive-gray to brown with a metallic gold, bronze or green cast to
the fore wings. Some may be brightly colored. The larvae are
cream-colored, legless grubs up to 1 1/2 inch long. The segment
behind the head is greatly widened. Larvae burrow beneath the bark
of shrubs and trees such as apple, ash, box elder, cherry, peach,
pear, pecan, raspberry, and roses. They are usually host specific. |
|
Flatheaded borers invade most commonly where the trunk
of trees or bark of shrubs has been sunburned or otherwise
damaged. The best way to avoid infestations is to protect young
plants from sunburn and keep older trees sound. Prune out infested
material and destroy it. Insects that are hidden within the wood
are not accessible to chemical sprays. |
|
Ocotillo Borer
Related to the flatheaded borers that attack roses and apples,
the ocotillo borer is a species that attacks only ocotillos. The
adults lay eggs into the bark, and the legless larvae mine into
the cambium, causing rapid decline of the plant. They seem to
prefer plants which are stressed, particularly newly planted
ocotillos. |
|
Avoid planting new ocotillos during the summer, when
adults are active. Cut any branches that do not leaf out below the
leafless area and dispose of immediately (the beetles can survive
in cut portions). If the plant does not leaf out in the spring,
inspect for grubs and if present, dig it up and dispose of
immediately. |
|
Round-headed Borers
The adults are called long-horned beetles because their antennae
are often as long as or longer than their body. Some may reach
lengths of four or five inches. |
Round-headed Borer |
One common species is the locust borer, which is black
with yellow stripes, and mimics a wasp. The larvae bore in solid
wood of plants such as apple, hickory, locust, mesquite and
poplar. They are legless cream or white grubs which are uniform in
width (the segment behind the head is not enlarged). |
Borers generally attack weakened trees and shrubs. They
may be prevented by keeping trees and shrubs in their best
condition. An exception is the mesquite twig girdler, which
girdles and kills small twigs of mesquite trees. The female beetle
then lays an egg in the section that is killed and the immature
develops within the wood. |
Palo Verde Beetle |
ROOT FEEDERS |
Coleoptera
Palo Verde Beetle
Immatures (grubs) feed on the roots of Mexican palo verde and
other non-native trees, and are six inches long when mature. They
spend up to three years underground. Adult beetles are four to six
inches long with long antennae and a "collar" of spines
on the thorax. They are active in July. |
Currently there is little that can be done to control
these beetles. They attack stressed trees, so the best prevention
is to keep trees as healthy as possible. |