Guard your tomatoes

The brown stink bug (Euschistus servus) is a plant-feeding insect that can cause substantial damage to tomato fruit in greenhouses. Female stink bugs lay barrel-shaped eggs in groups of 10 to 25, usually on leaf undersides. Nymphs are wingless, brightly colored or multicolored, and round. Later in development, nymphs are less brightly colored and resemble adults. There are five nymphal instars. Adults are winged and shield-shaped, approximately 1/2 to 5/8 (1.3 to 1.6 cm) inches in length, with a distinct triangle on the back (Fig. 1).

Stink bugs primarily attack green tomato fruit but will also attack mature fruit. Adults and nymphs use their piercing-sucking mouthparts to feed on fruit (Fig. 2) and succulent plant parts like leaves and stems by withdrawing plant fluids. Feeding damage to mature fruit looks like pinpricks or small dimples (Fig. 3) that may be surrounded by a yellow or white halo. Fruit damage is caused by the removal of fluids from cells and the injection of digestive enzymes. Extensive feeding damage can reduce marketability of fresh market tomatoes. The brown stink bug overwinters as adults in crop debris or leaf litter.

Stink bugs can migrate from weeds located outside into unscreened greenhouses. Treatment with a contact insecticide registered for use in greenhouses and on tomatoes may be warranted when stink bugs are feeding on tomato fruit. The insecticide Azera [active ingredients are azadirachtin and pyrethrins (MGK)] is labeled for use against stink bugs in organic production systems. Consult your state or university-based entomologists for insecticide recommendations. Scouting will help detect stink bugs early in the cropping cycle and time insecticide applications. However, stink bugs will drop off plants when disturbed.

Raymond is a professor and extension specialist in horticultural entomology/plant protection in the Department of Entomology at Kansas State University. His research and extension program involves plant protection in greenhouses, nurseries, landscapes, conservatories and vegetables and fruits. rcloyd@ksu.edu or 785-532-4750