Tarnished plant bug (Lygus lineolaris)
Biology and life history: Lygus bugs such as tarnished plant bug (L. lineolaris) and western tarnished plant bug (L. hesperus) are important pests in the Pacific Northwest agroecosystems that can attack a wide range of non-crop plants and crops such as grains, vegetable crops, and row crops. Adults are about ¼ inch long with flattened body, whose color varies from black, greenish, or pale yellow with few black markings to reddish brown. The color pattern makes a “V” shape behind the head. Adult female lays eggs inside plant tissues. Eggs develop into adults through five nymphal instar stages. Depending on the climate, tarnished plant bug can have several generations per year. Adults overwinter in leaf litter, under bark, or in dry mulches. Adults become active in early spring and start feeding available young plant parts.
Host plants and crop damage: Tarnished plant bug is a highly polyphagous pest known to feed on up to 700 crops, weeds, or wild plant species in North America. Using their piercing-sucking mouthparts, plant bugs penetrate plant tissue, release toxic saliva, and suck sap, injuring both vegetative and reproductive buds. The plant damage or sap oozing may facilitate disease development. Alfalfa, potato, and canola are the most frequently reported crops in the Pacific Northwest that are affected by these insect pests. Lygus bug feeding on lentils produces a characteristic cosmetic injury to the lentil known as chalky spot. It may produce this injury to dried pea as well, although it is economically less important. It is an important pest of alfalfa grown for seed, reducing yield.
Management: Integrated pest management guidelines and economic thresholds have not been fully developed for tarnished plant bug in the Pacific Northwest region. Regular field monitoring and sampling in the early stages of crop development is important to detect and timely manage these pests. Sampling can be done using sweep nets, sticky cards, or vacuums. Regular vacuuming is known to be effective to reduce populations but could also remove beneficial insects. Natural enemies such as big-eyed bugs, damsel bugs, minute pirate bugs, spiders feed on the nymphal stages of tarnished plant bug. Several parasitoids are known to attack eggs and nymphal stars. Controlling alternate hosts such as broadleaf weeds can help managing tarnished plant bug. Stubble or fall plant debris management may help reducing egg laying and overwintering sites.