Tobacco Thrips
Frankliniella fusca (Hinds), Thripidae, THYSANOPTERA


DESCRIPTION

Adult - Two forms of tobacco thrips adults occur, one with shorter wings than the other. Both adults are yellowish-brown and about 1 mm long.

Egg - The minute, whitish egg is concealed within plant tissue.

Larva - The yellowish-orange larva varies from 0.25 mm to 1 mm in length.

Pupa - The pupa ranges in length from 0.6 to 1 mm. Its body is yellowish-orange, but the wing pads and legs are pearly white.


BIOLOGY

Distribution - Tobacco thrips are distributed throughout the United States and are found in all North Carolina counties.

Host Plants - Tobacco thrips attack bean, cocklebur, cotton, crabgrass, dewberry, Irish potato, oat, peanut, pea, tobacco, tomato, and many other plants.

Damage - Several species of thrips damage peanut leaves, but the tobacco thrips is the principal, damaging species in North Carolina. Flower thrips, F. tritici (Fitch), sometimes feed on the flowers but do no economic damage. Thrips are most damaging to young peanut plants. As the upper surfaces of developing leaflets unfold, they appear scarred and even deformed. Farmers often refer to these damaged leaves as "possum-eared." Damage is usually minor but, with heavy insect infestations in combination with other stresses, stunting occurs during early development and the damaged peanuts recover slowly.

Life History - In North Carolina, tobacco thrips probably overwinter as adult females under ground litter or in other protected places. In the spring, adult thrips migrate to peanuts from small grain crops, grasses, and weeds. Each female deposits 50 to 60 eggs in the tissue of the foliage. They hatch in about 7 days. Apparently, unfertilized eggs produce males and fertilized eggs produce only females. Larvae (two stages) feed for 5 to 6 days before pupating either on the plant or in the soil. In 3 to 4 days, the adults emerge and begin feeding. Total development time from egg to adult is about 16 days. Five overlapping generations per year have been reported in South Carolina, and a similar number probably occurs in North Carolina.


CONTROL

Heavy rainfall is one of the most effective natural controls on tobacco thrips, although predaceous insects are also of some value. Chemical control of this pest is not difficult. In the Southeast, thrips are controlled throughout the season by systemic insecticides applied at planting. For specific insecticides and rates, consult the current North Carolina Agricultural Chemicals Manual.