Issue 11, July 7, 2015

Fourlined Plant Bug

Fourlined plant bug, Poecilocapsus lineatus, is a pest each year on a variety of herbaceous plants. Damage appears as contorted leaves with brown to black spots. Frequently, the spots are numerous enough to coalesce into large areas that may consume half or more of the leaf. Plants that are attacked include mint, chrysanthemum, coreopsis, dahlia, veronica, Artemisia, salvia, astilbe, cranesbill geranium, black-eyed Susan, and penstemon.

Fourlined plant bug adult on mint.

Close observation reveals the red nymphs hiding in the leaf axils. They grow to about ¼ inch long. They molt into ¼-inch-long adults that are greenish yellow, with four black stripes running the length of the body. The adults are very active runners and fly readily when disturbed. They are obvious on the plants because they do not hide. By the end of June, they will have mated and inserted their eggs into plant stems where the eggs will remain until hatching next spring.

Close up image of fourlined plant bug damage on mint.

Insecticide sprays are effective against these insects, but good coverage is essential. Avoid spraying when the plants are in flower to avoid killing pollinating insects. Acephate (Orthene), bifenthrin (Talstar), carbaryl (Sevin), and cyfluthrin (Tempo) are effective. Insecticidal soap will also be effective with very good coverage and is probably the only option if the bugs are on mint used in food. Because the eggs overwinter in the stems, removing plant debris in early spring should reduce their numbers. (Phil Nixon)

Phil Nixon

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