PESTS OF GARDENS AND ANNUAL FLOWERS

Coleoptera

Flea Beetles
Several species of flea beetles occur in Arizona. The adults range from 1/16 to 1/4 inch long and are various colors, including black, greenish or bluish black, green or yellow. They have enlarged hind legs which enable them to jump like fleas. They feed on the leaves of potato, young corn, carrot, cauliflower, bean and other related vegetables. One species attacks Mexican primrose, giving it a tattered appearance. Another brownish-black species attacks Dichondra lawns.

The larvae are slender white worm-like creatures that usually feed on roots and stems underground.

Mexican Bean Beetle
The adults are reddish coppery brown with eight black spots on each hind wing. They are 1/4 to 3/8 inch long and resemble predaceous lady beetles. Mexican bean beetles are more common above 3,000 feet.

The larvae are yellow with black-tipped spines. They are about 1/3 inch long when full grown. Both adults and larvae feed on the leaves of beans, especially snap and lima beans. The egg masses are orange in color, and difficult to tell from those of predaceous lady beetles.

To prevent bean beetle attacks, plant bean varieties that bear before Mexican bean beetles are active in your area.

Vegetable Weevil
The adults are brownish-buff weevils about 1/2 inch long, with a V-shaped white marking on the rear of the wing covers. The larvae are cream colored and legless. They attack carrots, celery and other vegetables during the winter and early spring. The adults also feed on the foliage of various vegetables in the spring.

Lepidoptera

Armyworms

Beet Armyworm: The adult moths are drab gray with black markings and about 3/4 inch long. The larvae are pale green or olive with dark and light stripes along the back and grow up to 1 1/4 inch long when mature. They may resemble cabbage looper larvae, except they have four pairs of abdominal legs (prolegs), whereas cabbage loopers have only two pairs.

Fall Armyworm: Adult fall armyworms are 3/4 inch long, ash-gray moths. The youngest larvae are white with a jet-black head. The larvae tend to darken as they grow, until they are green to almost black and about 1 1/2 inches long. The front of the head is marked with an inverted Y.

Yellow-Striped Armyworm: The adult moths have a wing span of 1 1/2 inches. The front wings are mottled dull brown, blue-gray, yellow-gray and white. The larvae are velvety black with yellow stripes along the sides and reddish underneath. They may reach two inches in length.

Cabbage Loopers
The adults are brown and gray moths with a wingspan of 1 1/2 inches. They have silver spots on their upper wings, towards the center of the wing.

The larvae are pale green caterpillars up to 1 1/2 inches long. The larvae have two pairs of abdominal prolegs, unlike the armyworms. They feed on beets, broccoli, Brussels sprouts, cauliflower, celery, collards, kale, lettuce, peas, potatoes, radishes, tomatoes, and turnips.

Corn Earworm (also called the tomato fruitworm, cotton bollworm and tobacco budworm)
Adults are green to brown moths with a wingspan of 1 1/2 inches. Full-grown larvae vary in color from shades of green, red, or brown with light and dark stripes running the length of the body. They feed on beans, corn, lettuce, potatoes, tomatoes, and certain flowers, as well as cotton and tobacco.

The eggs are laid on corn silks. The larvae first feed on the silks and leaves, and eventually make their way into the kernels at the tip of the cob. While they feed they produce copious amounts of frass, which is a sign of infestation. Once mature, the larvae drop from the plant and pupate in the soil.

Cutworms
Several species of cutworms may be pests in gardens (they may also be pests of turf). Cutworms are inactive during the day, hiding under clods of soil. The larvae are dark gray, brown or black and may be up to two inches long. They tend to curl up tightly when disturbed. The caterpillars cut off new seedlings or early season plants above, at or below the soil surface.

Diamond-Back Moth
Adults are slender brown moths with a wingspan of 1/2 inch. When their wings are folded together over their back, it forms a white diamond-shaped marking on the top. The larvae are slender and light-green with black hairs or spines. When disturbed they wriggle rapidly, and often drop from the plant by a silken thread. The pupae are often found rolled up in the edges of leaves. They produce a delicate silken cocoon about 1/2 inch long, and spindle shaped.

Salt Marsh Caterpillar (also called "woolyworms")
The adults are moths with white forewings and yellow-orange hind wings. Both sets of wings are peppered with black spots. The larvae are up to two inch long caterpillars, brown or buff colored with numerous long dark hairs. They often build up in the fall, sometimes crossing roads in high numbers.

Southwestern Corn Borer
The larvae are up to 1 1/4 inch long and are white, often with a peppering of darker spots during the summer. They feed on sweet corn, field corn, popcorn and sorghum. The young larvae feed on leaf surfaces, producing transparent or skeletonized areas. They also may feed in the leaf whirls of young corn plants, destroying the growing tip. The older larvae bore down into the stalks, causing them to break. The adult moths have buff-colored front wings and white hind wings.

Squash Vine Borer
The adult is a wasp-like moth with copper-green forewings 1 to 1 1/2 inches across, and with fancy, heavily furred hind legs. The larva is white with a brown head. The larvae tunnel in the vines of squash, pumpkins, various kinds of melons, etc.

Signs of infestation are coarse yellow castings pushed out through holes, and vines that suddenly wilt and die. To remove borers, slit infested vine with a sharp knife and destroy the larvae. Cover the affected area with soil to encourage supplementary rooting.

Tomato Hornworm (or Tobacco Hornworm)
If you have planted tomatoes, you have probably seen these larvae. They can grow to three to four inches and have a projection that resembles a horn at the end of their abdomen. The true tomato hornworm larva is green with diagonal white lines on the side of each segment that form L-shapes. They pupate in the soil, forming a reddish-brown pupa at least three inches long. The adults are large gray moths with a wingspan of five inches. They have four yellow-orange patches on each side of their abdomen. The adults are commonly called sphinx or hawk moths.

Two other sphinx moths that closely resemble the tomato hornworm are the tobacco hornworm and the white-lined sphinx. The tobacco hornworm is also found on tomatoes, but has a red "horn" and straight diagonal stripes. It is actually more common here than the tomato hornworm. The larvae of white-lined sphinx moths also may be mistaken for hornworms, but they lack the diagonal body stripes. They consume a number of different host plants, and may build up to high numbers in the desert in the fall.

Pick off and destroy any larvae you see.

Diptera

Leaf Miners
Leaf miner damage shows up as light-colored "trails" in the surface of a leaf. The damage is caused by yellow fly larvae (maggots) that tunnel within the leaves, removing tissue. The adults are minute flies about 1/16 inch long. They are black with yellow markings. The damage is usually minor, although high infestations may occur in lettuce. Control is not recommended.

Hemiptera

Harlequin Bug
Adult harlequin bugs are brick red to yellowish with black markings. These insects belong to group commonly known as "stink bugs," because they have scent glands that produce disagreeable odors when they are threatened. The females lay their eggs (which look like miniature barrels) in crops in the spring. The nymphs are green and suck sap from plants. These pests cause discoloring where they feed, and when abundant, may cause leaves to wilt, turn brown and die.

Harlequin bugs feed on crucifers such as Brussels sprouts, cabbages, cauliflower, collards, cress, horseradishes, kohlrabi, mustard, radishes and turnips. They also eat asparagus, beans, corn, eggplants, and potatoes. They are found more commonly at the higher elevations.

Squash Bug
Squash bug adults and nymphs attack the vines and fruits of cucurbits, such as zucchini and summer squash. The adults are dark brownish-black and about 5/8 inch long. The nymphs are marked with bright red. Squash bugs, as with other true bugs, give off a disagreeable odor when pinched.

Destroy any bugs found. Cover immature plants with cones of window screen or row covers where bugs are active.

Aphids
Most aphids have projections at the rear of the abdomen called cornicles. They are known for their ability to build up to high numbers relatively rapidly. Species found in gardens include:

Green Peach Aphid - Adults are over 1/8 inch long with relatively long legs and are a deep pea-green color. They feed on alfalfa, and vegetables such as beans.

Cotton or Melon Aphid -These aphids vary in color from pale yellow to dark grayish-green. They feed on cucurbits as well as cotton.

Cabbage Aphid -Adults are dull green to powdery blue, with a waxy covering that gives them a grayish white appearance. Adults and nymphs feed on crucifers such as cabbage, broccoli and cauliflower.

Several biological control agents feed on aphids, including lady beetle adults and larvae, lacewing larvae, and syrphid fly larvae. They also may be washed off plants using water or soap and water solutions. Be careful on hot days, because water may "burn" plants. Some plants may be sensitive to soap as well.

Potato Psyllid
Adults are about 1/8 inch long with dark, grayish-brown bodies marked on the top with white markings. The wings are held together over the abdomen. They resemble miniature cicadas. Both adults and nymphs have well-developed hind legs for jumping, and they are sometimes called "jumping plant lice." They inject a toxic substance into the plant that causes yellowing of plants. All stages feed on potato, tomato, and related plants such as peppers.

Whiteflies
Adult whiteflies are less than 1/16 inch long and covered with a whitish, waxy powder (under a microscope it is apparent their bodies are actually pale yellow). The oval, flattened immatures settle down and feed on the underside of leaves, often creating sticky beads of "honeydew." The most prolific type of whitefly is the sweet potato whitefly. Other species found in Arizona are the ash whitefly and the greenhouse whitefly, which may require special controls.

Although when the numbers are high in the fall sweet potato whiteflies appear to be on every single plant in the yard, they tend to feed and develop on a more limited number of plants. Hibiscus, lantana, and annual herbs and vegetables seem to be preferred hosts. Target control measures at these types of plants. To avoid problems, delay planting fall vegetables until temperatures begin to decline and whitefly numbers drop.

Phylum Mollusca

Snails and Slugs
Slugs and snails feed on plants in a way that may be mistaken for insect damage. One way to tell if they are present is to look for the glistening "slime trails" they leave behind on foliage and the ground.

Slugs and snails are active at night and hide under boards, debris, etc. during the day. One way to trap them is set out boards, or pieces of cardboard between rows and remove any slugs or snails that hide under them. Another way to trap them is to leave out pans of beer. The snails and slugs climb in and drown. In a garden setting, a barrier of diatomaceous earth (available at pool supply stores) may be sprinkled around the base of susceptible plants. If the problem is extensive or costly, molluscicidal baits are available at lawn and garden supply stores.

One common species is the brown garden snail. It is an introduced species that thrives in cultivated areas. It is about 1 inch in diameter when full grown, and has a rounded, brown and beige mottled shell. Another common snail is the decollate snail. This species is unusual because it is both a predator and a pest. In Southern California it is sold as a predator to control the brown garden snail. Where its prey is absent, however, the decollate snail becomes a serious pest of emerging seedlings and bedding plants. Decollate snails have an elongate, spiraling shell.