February 25, 2018

Western flower thrips causes damage to non-low tunnel fruit

During the August 2014 harvest period, we noticed fruit damage from western flower thrips.  Western flower thrips are slender, very small insects, about 0.03 inch long when mature.  Adults have feathery wings and vary in color from yellow to dark brown; nymphs are white or yellowish with small dark eyes.

Thrips feed on strawberry blossoms, which causes the stigmas and anthers to turn brown and wither prematurely, but not before fertilization has occurred.  As fruit develops, thrips feeding may cause a russeting or bronzing of the fruit.  

An easy way to monitor or sample for thrips is to place randomly collected flower blossoms in a zip-lock plastic bag and locate in a very warm area.  We placed the plastic bag on the dash of our vehicle.  After one hour, remove the blossoms and shake them onto black paper.  If thrips are present, you should be able to spot the small cigar shaped insects moving on the paper.

Our method of control was applying Mycotrol, an organically approved insecticide, at 1 tablespoon per 1 gallon of water, which was applied every 5 days from mid to late August before we saw an improvement in fruit quality.