Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
Harlequin bugs are being seen in especially high numbers this season. They are a pest of many vegetables, but preferentially feed on and damage brassica plants, which includes mustards, crucifers, greens and radish. They also are secondary pests of various fruit and vegetable crops such as beans, cantaloupe, onion, raspberry and even tomato.
Females will lay about 12-barrel shaped eggs in a cluster (Fig. 1). The eggs are easily recognizable by their black and white pattern. Eggs laid now will hatch in 4-5 days. Nymphs feed for a moderately long period of time of 5-8 weeks going through 5 to 6 instars. The whole process from egg to adult can take 45-75 days.
Harlequin bugs suck. They insert their needle-like mouthpart into plant tissue and suck out fluids, which destroys plant tissue and potentially kills plants, particularly young plants. Damage appears as stippling or light-colored cloudy spots in leaves (Fig. 2). Young plants will have larger areas of plant tissue with dead patches, wilting and deformed growth.
Physical removal of eggs, and the bug itself can reduce the pest population without the need for insecticides, although this method works best in smaller operations or organic systems. Harlequin bugs can be controlled chemically by using neonicotinoids or pyrethroids or in organic systems using Spinosad’s. Keep in mind that insecticides are more effective against nymphs than adults. Read and follow the label for proper use.
Fig. 1 Harlequin bug eggs, nymphs and an adult
Fig. 2 Harlequin bug damage to broccoli leave
