Scouting Tips for Onion Thrips in Onions
Christy Hoepting, Extension Vegetable Specialist
Cornell Vegetable Program
Last Modified: July 1, 2023
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.
Scouting Tips for Onion Thrips in Onions (pdf; 239KB)