Thrips

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Roberts, P. M. and G. K. Douce, Coordinators. 1999. Weevils and Borers. A County Agent's Guide to Insects Important to Agriculture in Georgia. University of Georgia, Col. Ag. Env. Sci., Cooperative Extension Service, Tifton, GA, USA. Winter School Top Fifty Agricultural Insect Pests and Their Damage Sessions, Rock Eagle 4-H Ctr., Jan. 20, 1999.

Contents

Description

Several thrips are economically important in Georgia. The western flower thrips (Frankliniella occidentalis) and the tobacco thrips (Frankliniella fusca) are two very destructive species. Adult thrips are usually less than 2.0 mm in length. The adult western flower thrips is yellow or yellow-orange; the tobacco thrips adult tends to be dark brown to black in appearance. Adult thrips have two pair of fringed wings. Larvae are very small at about 0.25 mm in length. They are white or cream-colored during the first instar, turning more straw-colored during later stages. There is a pupal stage that occurs in the soil.

Hosts

Thrips have a wide host range. Most vegetables, agronomic crops, ornamentals, and weeds have one or more thrips species that may attack them.

Damage

Thrips cause noticeable damage to seedling stage plants. They rasp the leaves and terminal buds with their sharp mouthparts and feed on the escaping juices. Leaves may turn brown on the edges, develop a silvery color, and may become distorted and curl or cup upward. Early, moderate to severe thrips injury can delay maturity. The main seedling thrips in Georgia are the tobacco and onion thrips. The western flower thrips feeds on the blooms and fruit of many plants. They cause various types of mechanical injury to the fruiting structures. These include pits, buckskin, black specks, raised blisters and cat-facing. Western flower, tobacco and onion thrips transmit tomato spotted wilt viruses on several crops. This is the more significant damage caused by thrips. Some of the crops affected severely by TSWV are tobacco, peanut, tomato and pepper.

Life Cycle

Thrips have a unique life cycle. The adult lays her eggs in plant tissue. The larvae hatch and enter two (maybe more) instars before entering the pre-pupal and pupal stage in the soil. The pupae emerge as winged adults and migrate back to the plants or out of the field. The entire cycle from egg to adult requires from 12 to 16 days.

Control

Thrips can be controlled with insecticides even though western flower thrips is tolerant of several insecticides and is the most difficult one of the three species to control. Each crop has different treatment thresholds.

4387048
Photo by Jack T. Reed, Mississippi State University, Bugwood.org
Adult western corn thrip on cotton.
View in Bugwood Image Database
Adult western corn thrip on cotton.
1243058
Photo by Whitney Cranshaw, Colorado State University, Bugwood.org
Nymphs of onion thrip at base of onion leaf.
View in Bugwood Image Database
Nymphs of onion thrip at base of onion leaf.
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