Insect Note #42 (Revised)

Prepared by:
K. A. Sorenson and K. A. Kidd, Extension Entomology

Dated 4/94
Placed on the Web 4/95 by the Department of Entomology, NCSU

True Bugs in the Field and Garden

Hemiptera:
The term "bug" is commonly applied to all insects, but only those insects belonging to the order Hemiptera are true bugs. Several features distinguish bugs from other insects, especially the wings and the mouth parts. The base of the forewing is thickened and leathery while the outer portion (tip) is membranous. Hindwings are completely membranous. At rest, the wings are held flat over the insect's abdomen with the tips overlapping. The mouth parts form a beak used for piercing and sucking. Bugs feed on a variety of plants and animals, but the ones of most concern to growers and gardeners are those which attack crops.

Bugs most commonly attacking vegetables are the squash bug, harlequin bug, stink bugs, and tarnished plant bug. Another frequently seen bug is a predatory stink bug which preys on other insects.

Squash Bug

Squash bugs feed on all cucurbits, but prefer squash and pumpkins. Adults and nymphs feed in colonies, sucking plant juices, and injecting a toxic substance which causes vines to turn black and dry. When infestations are heavy, small plants and individual runners may be destroyed, fruit may not form, and, if it does, bugs may feed on it.

Squash bugs overwinter as adults and in the spring fly into gardens and mate. The dark brownish-gray oval-elongate adults (about 5/8 inch long) are often found in pairs on the undersides of leaves or around the base of plants. Bronze-colored eggs are laid in groups usually on the undersides of leaves, in the angles formed by leaf veins.

Nymphs which hatch from the eggs are green with rose-colored to dark appendages. Larger nymphs are grayish white with dark heads, legs and antennae. Wing pads are visible on the last two instars. Five to eight weeks are required for development from egg to adult. Only one generation occurs each year, but because of the extended egg-laying period, adults and nymphs are present throughout the summer.

Small boards or shingles placed near plants provide a nighttime gathering place for squash bugs, which can be removed and destroyed in the morning. Other cultural practices which lessen damage from this bug include proper fertilization for a vigorous crop, destruction of crop debris, and growing resistant varieties such as Butternut, Royal Acorn, and Sweet Cheese. Handpicking adults and/or leaves with eggs is recommended for small gardens. If chemical control is needed in commercial squash plantings, use carbaryl (Sevin) 50WP, 80WP, 4XLR, or 5D at a rate of 1 lb ai/acre; endosulfan (Thiodan) 2EC or 50WP at 1 lb ai/acre; or esfenvalerate (Asana) XL, 0.66EC at a rate of 1 lb ai/acre. Carbaryl and endosulfan have a 0 day waiting period and esfenvalerate requires 3 days between last application and harvest. In home gardens, use carbaryl, endosulfan, naled (Dibrom) 60EC (2 tsp/gal spray) or malathion 57EC (2 tsp/gal spray). Waiting periods to harvest are: carbaryl, 0; endosulfan, 0; naled, 0 - summer squash, 1 - winter squash and malathion, 1 - squash, 3- pumpkin.

Spray when nymphs are small. Young nymphs are the most susceptible stage to insecticides, while adults are difficult to kill.

Harlequin Bug

Harlequin bugs feed on nearly all crucifers (cole crops) including related weeds. As do all true bugs, they suck with the needlelike mouth parts, extracting plant juices from stalks, leaves or veins. Damage is first visible as irregular light areas around the feeding site, then plants become stunted or wilt, turn brown, and die.

Adult harlequin bugs are shield-shaped, about 1/2 inch long and black with bright orange, red or yellow markings. This stage overwinters among plant debris, emerging in the spring to feed then lay eggs. Barrel-shaped, black and white eggs are laid in double row clusters. Nymphs are oval shaped with coloration similar to adults, but are smaller and wingless. Depending on temperature, 7 to 11 weeks are required for development from egg to adult. Two to four generations occur each year.

Because adults overwinter in field debris, plowing after the weather turns cold will reduce populations. Weeds in fields and along fence rows should also be destroyed. Varieties which show resistance are: Copenhagen Market 86, Headstart, Savoy Perfection Drumhead, Stein's Flat Dutch, and Early Jersey Wakefield (cabbage); Green Blaze (collards); Snowball X and Snowball Y (cauliflower); Red Devil, White Icicle, Globemaster, Cherry Belle, Champion, and Red Prince (radish). For chemical control, refer to the most recent N. C. Agricultural Chemicals Manual.

Stink Bugs

Two kinds of stink bugs, brown and green, are commonly found attacking vegetables. They feed on a large variety of plants, although the preferred hosts are wild plants. They build up on weeds, then move to vegetables and other cultivated plants such as beans and cowpea (seeds), okra (pods), tomato (fruit), melon (stems), and asparagus. Catfacing of apples and peaches and kernel spot of pecan are the results of stink bug feeding.

Nymphs of brown stink bugs are green. One or two generations occur each year with peak populations in late September to early October.

For chemical control, refer to the most recent N. C. Agricultural Chemicals Manual.

Tarnished Plant Bug

Tarnished plant bugs feed on a wide variety of field, fruit, and vegetable crops and many common weeds. Feeding occurs on buds and terminal growth, causing new growth to be yellowed and distorted. Fruit feeding results in catfacing, that is dimpling around the feeding site.

Adults overwinter in plant debris and after emerging in the spring, females lay eggs in stems, petioles, buds or flowers of plants. Nymphs which hatch out are yellowish-green, about 1/25 inch long and oval with long legs and antennae. Larger nymphs have 4 black dots on the top of the thorax and one on the abdomen. Nymphs molt 5 times, becoming adults which are brown, mottled with bronze, white, yellow, reddish-brown and black. A white triangle between the "shoulders" is characteristic. They are about ¬ inch long and oval in shape with long appendages.

Two-Spotted Stink Bug - A Beneficial Insect

True bugs are commonly seen attacking a wide range of hosts. Sanitation should be used as a management tool against all of these bugs together with chemical control. Small nymphs are generally more susceptible to insecticides than are large nymphs and adults; for the most effective control, target sprays against the young stages. When using insecticides, always follow label for rates and precautions.

The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsements by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. All pesticide recommendations provided in this publication apply to pest control in North Carolina. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain information about product usage in your locale and examine a current product label before applying any chemical. The information presented on pest biology is based on conditions in North Carolina and may not be applicable to your locale. For further information, we recommend that you contact the Cooperative Extension Service office in your county.