Western flower thrips
Frankliniella occidentalis
(Thysanoptera: Thripidae)


Western flower thrips are slender, very small insects, about 0.03 inch long when mature. Adults have 4 feathery wings and vary in color from yellow to dark brown; nymphs are white or pale with small dark eyes.

Biology and damage:

Both nymphs and adult thrips can injure the plant by rasping the plant bud, flower, leaf tissues and then sucking the exuding sap. Thrips feeding on strawberry blossoms cause the stigmas and anthers to turn brown and wither prematurely, but not before fertilization has occurred. With high popuylaitons, the surface of the berry may become cracked and discolored (see image).  Although the flower thrips are often numerous on strawberries when catfacing occurs, thrips do not cause catfacing. This is a result of lygus bug feeding and possibly other factors. As fruit develops, thrips feeding may cause a russeting of the fruit around the cap. This type of injury is seldom economic.
There can be numerous generations each year. Adults become active in early spring and deposit their eggs into plant tissues. Full development from egg to adult takes place in approximately 2 weeks.

Field scouting/monitoring:

Control is not usually necessary because western flower thrips rarely cause economic damage. Sprays applied to control thrips disrupt biological control of other pests such as twospotted spider mites and lygus bugs. Consider treating only if populations reach 10 thrips per blossom (UC-Davis). To sample thrips, place randomly collected flower blossoms into a glass container charged lightly with ethyl acetate. After at least 30 min, count the thrips by removing the blossoms and shaking them onto black paper.



Virginia home spray guidelines
California guidelines


Minute pirate bugs and other generalist predators can be important natural enemies of thrips.