Pest of the Week, 9/08/09

Common name: Onion Thrips

Latin Name: Thrips tabaci


Life Cycle: All stages overwinter, mainly winged, yellowish-brown female populations (males are rare), eggs laid and hatch 5-10 days later, nymph, pupae, then adult -> entire life cycle is complete in 14-30 days, dependent upon temperature; the warmer the temperature, the shorter the life cycle. Thrips thrive in hot, dry weather.

Plants effected: Onion, garlic, and their relatives, crucifer crops - can cause enough damage to decrease yield or deem crops not harvestable; pest has chewing sucking mouthparts, rasping the plant tissue cell by cell and sucking up the juices; feed deep in leaf axils. Insects are small and hard to see, damage is commonly seen before pest.

Insect Habit: Overwinters as an adult in weed edges or crop leaf residues; populations can explode on crops when weed edges or alfalfa plantings nearby are mowed

Control: Good crop rotation, Entrust (be sure it is applied and runs into the bases of the leaves), sticky traps to monitor (thrips are attracted to yellow and white), irrigate crops, mixing carrots and onions in the same planting may help decrease numbers, grow onions that have resistance (onions with open leaf habit rather than tight-growing leaves), remove volunteer onion plants; because of short life cycle, resistance to chemicals is prevalent; try to reduce chemical control measures