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)

Upcoming Events
Chipping Potato and Field Crops Twilight Meeting
August 27, 2026
Dansville, NY
This year, our field meeting is bringing together field crops and chipping potatoes. SWNY Dairy, Livestock, and Field Crops Specialist Katelyn Miller will lead a field crops management discussion. Hear the latest updates in potato disease control and see the Cornell chipping potato variety trial run by Walter De Jong. Dinner follows the educational event.
1.5 DEC credits available in 10, 1a, 21, and 23.
IPM Field Day for Urban Growers
September 10, 2026
Buffalo, NY
Join us for a hands-on field day exploring integrated pest management and season extension tools for urban growing spaces and the opportunity to build community with local growers!
This event will focus on best practices for using row covers and rat mitigation. Check out our CCE demonstration trial using insect exclusion netting to manage swede midge, an invasive fly that causes damage to brassica crops. Explore how to identify rat activity, reduce attractants, and strengthen site management. Hear from local growers on how they manage pests with a focus on organic management and how they extend the season on their farms and gardens.