Kelly Jackson
Christian County Extension Office
Plant Bugs
The world is full of plant bugs. For the most part, these sap feeders go about their lives in relative obscurity. However, the distinctive marks that result from infestations of some species can ruin the appearance of landscape plants and garden herbs. Usually, infestations are noticed only after significant damage is done. Symptoms and specimens of two common species will soon be showing up in gardens.
The adult four-lined plant bug is a yellow or bright green insect with 4 black stripes on its back and a black diamond-shaped mark at the end of its body. The smaller, wingless nymphs, or immature insects, vary from red to yellow and also have black markings. These insects use their piercing-sucking mouthparts to feed on more 250 different mostly herbaceous plant species.
A dark brown to black, 1/16- inch diameter spot appears at each feeding site. Saliva injected as the insects feed kill surrounding tissue, which eventually dies and drops, leaving small holes. The damage is most intense on the new growth This gives leaves a spotted appearance or “lacy” appearance. Generally, feeding and damage symptoms first appear at the top of the plant and can be confused for a disease.
When the plant is disturbed, adults fly away or hide on the underside of the leaves. The wingless nymphs are can only run or hide. Both stages may be overlooked but the damage symptoms are very obvious and detract from the appearance of the plant. Control measures should be taken when the first leaf spots are seen. Insecticidal soap or pyrethrins can be used as contact spray but the insect must be hit with the spray to be successful. Repeat applications are needed. Be sure the product you select is labeled for the plants being treated, especially on herbs. Alternatively, a floating row cover also works well as a physical barrier.
Four-lined plant bugs overwinter as eggs that are laid in tender shoots or water sprouts. They hatch in mid-to late April and the nymphs take about 30 days to reach the adult stage.
Yucca plant bugs are brightly colored insects and occur wherever yucca is grown. These sap feeders produce small light spots on the leaves where they have used their sucking mouthparts. Large numbers of spots can produce yellow areas. A tarry black waste material is left on the leaves. Adults have wings but do not fly readily; they are more likely to run when the plant is disturbed. A direct spray of insecticidal soap should provide control. Check the label to determine whether or not the product can be used on yucca.
A third plant bug called the Tarnished plant bug, has a very wide host range. It emerges early in the spring and feeds on rapidly growing plants, especially vegetable and fruit crops like strawberry and tree fruits. The adults are about ¼ inch long and oval-shaped. They are brown to black with yellow or white patches. They are easy to identify by the yellow markings behind the head that vary from a V-shape to a Y-shape to a heart-shape.
They cause damage by inserting their piercing-sucking mouthparts into the flowers and young fruit. This kills the developing seeds and surrounding tissue resulting in a deformed fruit. Strawberries are especially damaged by this pest. Inspect for tarnished plant bug and either remove by hand or treat with an insecticide like permethrin, carbaryl, or malathion. Be sure to read and follow the label. Since tarnished plant bug overwinters in leaf litter, tall grass or weedy areas, keep lawn areas mowed and garden area clean.
