Tarnished plant bugs in large populations
Large populations of tarnished plant bugs are reported in southwestern Michigan. Tarnished plant bug feeds on a variety of vegetable crops, including asparagus, snap beans, lettuce celery and others. The adults are approximately one-third of an inch long, are bronze-brown with black markings and are extremely mobile. Adults may fly in and out of fields quickly (Most flight occurs in early morning and late afternoon/evening.), leaving only plant damage as evidence of their presence. Both adults and nymphs (which cannot fly, so are less mobile) feed by sucking juices out of plants. In asparagus, feeding by tarnished plant bug produces “tip die off” above the feeding site. In snap beans, tarnished plant bug feeding may produce flower abortion or feeding injury (brown spots) on pods. In celery and lettuce, feeding produces small brown areas of necrotic tissue which reduce quality and may promote secondary bacterial infections. Tarnished plant bug may also damage potatoes, tomato fruit, peppers and fruit crops.
Plants are most vulnerable to tarnished plant bug infestation when alternate hosts are less attractive. In most plants (weeds and cultivated) tarnished plant bugs prefer plants flowering and producing seed. Once weeds start to senesce and/or dry down, they become less attractive and large numbers of tarnished plant bug adults may move into nearby vegetable crops irrigated and growing vigorously. In addition, tarnished plant bugs move out of alfalfa fields (one of their preferred food) after it is cut or during prolonged dry periods.
Since tarnished plant bugs are so mobile, growers should scout fields by sweeping for adults and nymphs (preferably early in the morning) or inspecting their crops for signs of feeding damage. It may be beneficial for growers to sweep adjacent hedgerows and ditch banks. If large numbers of tarnished plant bugs are found on the weeds in these areas, you can expect that they may be moving into fields to feed. Consult Bulletin E-312: 2006 Insect, Disease and Nematode Control for Commercial Vegetables, for insecticides registered to control tarnished plant bugs on vegetable crops and for treatment thresholds for some crops. This bulletin can be viewed at http://veginfo.msu.edu.