Scouting Tips for Onion Thrips in Onions
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
To find the first thrips of the season, look deep into the leaf axils. Inspect 20 to 30 plants and count the total number of onion thrips (OT) per plant and divide by the average number of leaves per plant to get the number of OT per leaf. Thrips feeding causes silvery streaking along the leaves. If you can already see thrips feeding damage that is also a good indication that it is time to spray. If there is a lot of feeding damage, than you likely missed a timely first spray.
Adult onion thrips are the first thrips of the season. They are tiny brown, sliver-like insects up to 2 mm in length. Photo by C. Hoepting, CCE Cornell Vegetable Program
Onion thrips nymphs are yellow and 0.5 to 1.2 mm in length. Photo by Whitney Cranshaw, Colorado State University.
Subtle streaking along leaves is an early indication of early onion thrips feedling. This plant has reached the spray threshold. Photo by C. Hoepting, CCE Cornell Vegetable ProgramScouting Tips for Onion Thrips in Onions (pdf; 239KB)
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