Thrips on onions

Onion thrips (Thrips tabaci) are the most consistent insect pest of onion in the US, present in virtually every onion-growing region. Their small size and habit of sheltering deep in the overlapping leaf bases make them difficult to control even with targeted insecticides. Beyond direct feeding.

Onion thrips (Thrips tabaci) are the most consistent insect pest of onion in the US, present in virtually every onion-growing region. Their small size and habit of sheltering deep in the overlapping leaf bases make them difficult to control even with targeted insecticides. Beyond direct feeding damage, they vector iris yellow spot virus (IYSV), which has become a serious disease concern in commercial and home onion production.

I don't grow onions at my Long Island property, so this guide draws on Cornell Cooperative Extension, Penn State Extension, and UC IPM research.

The pest

Onion thrips (Thrips tabaci) is the primary thrips species on onions in North America, though western flower thrips (Frankliniella occidentalis) can also infest onions. Per Penn State Extension, T. tabaci:

• Adults: pale yellow, 1–1.5mm, with fringed wings
• Females reproduce parthenogenetically (without mating) in spring and summer — rapid population buildup
• Overwinters as adults in soil, weed debris, and alternative hosts
• Completes a generation in 10–20 days in warm conditions