Tarnished Plant Bug
Lygus lineolaris (Palisot de Beauvois), Miridae, HEMIPTERA


DESCRIPTION

Adult - Like most lygus bugs, the tarnished plant bug is oval in shape and has a characteristic white triangle between the "shoulders." Its legs and antennae are relatively long. The adult may be one of several shades of brown and is approximately 6.4 mm long.

Egg - The tiny elongate egg is slightly curved.

Nymph - The wingless nymph is yellow-green to green in color with several black spots on its back. Length varies from 1.5 mm to slightly less than adult size. The fourth instar nymph has wing pads.


BIOLOGY

Distribution - Tarnished plant bugs are generally distributed because warm, dry climates are most conducive to the buildup of lygus bug infestations, but tarnished plant bugs pose a limited threat in North Carolina. In states further south and southwest, economic injury occurs annually.

Host Plants - Tarrnished plant bugs infest over 50 economic plants including many field, forage, fruit, and vegetable crops. Also, weeds such as butterweed, fleabane, goldenrod, aster, vetch, dock, and dogfennel commonly harbor these insects in southern states.

Damage - Shiny circular spots of excrement on various plant parts indicate the presence of tarnished plant bugs. These bugs pierce buds and terminal growth with their needle-like mouthparts and extract plant juices. New growth may be yellowed and distorted, causing plants to appear unthrifty.

Life History - In North Carolina, adults hibernate in plant debris and resume activity in spring. At this time females insert eggs into succulent host plant tissue with their sword-like ovipositor. Eggs hatch 1-1/2 to 3 weeks later. The nymphs develop through five instars over a three-week period as they feed on plant sap. Mature nymphs molt and emerge as adults. The first few generations develop on preferred hosts such as small grains, alfalfa, wild grasses, vetch, dock, and fleabane. As hay is cut or as other plants dry out, tarnished plant bugs migrate in large numbers to succulent hosts such as cotton or vegetable crops. During summer, the life cycle (from egg hatch to adult emergence) is completed in 4 weeks. As many as 5 annual generations are possible.


CONTROL

Vegetable crops planted as far as possible from the forage and cotton crops preferred by this pest are not likely to be heavily damaged. Weed control and destruction of crop residue help eliminate sources of food and shelter for the tarnished plant bug. Chemical control should not be necessary; however, in the case of heavy infestations, consult the North Carolina Agricultural Extension Service for recommendations.

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