Onion Thrips Control

Symptoms

Tiny pale yellow to brown thrips rasp the leaf surface and suck sap, leaving silvery white streaks and patches on the leaves. Heavily attacked leaves develop a blasted, curled and distorted look and may dry from the tip. The plants look pale and stunted and bulb size is reduced. Thrips hide in the leaf axils near the base.

Damage

Onion thrips is the most serious pest of onion and garlic and can cause yield losses of 30 to 50 percent through reduced bulb size. The feeding wounds also open the door for purple blotch disease, and thrips injured plants show much higher disease severity. Hot dry weather favours rapid build up.

Organic & cultural control

Use blue sticky traps at about 15 to 20 per acre to monitor and trap adults. Spray neem oil or neem seed kernel extract repeatedly, which also helps suppress build up. Light irrigation and overhead sprinkling disturb thrips. Conserve natural enemies like predatory mites and Chrysoperla, and avoid planting onion next to wheat or other thrips hosts.

Chemical control

Recommended sprays include spinosad 45 SC, fipronil 5 SC, or a profenophos based product, used in rotation with a sticker to ensure coverage in the waxy leaf axils. Thrips develop resistance quickly so never use the same group repeatedly and alternate modes of action. Use only labelled products at the correct dose, add a recommended wetting agent, follow the pre-harvest interval and consult your KVK or agronomist before spraying.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Plant healthy thrips free seedlings and avoid fields next to onion, garlic, wheat or clover that carry thrips. Keep balanced nutrition and avoid excess nitrogen which favours thrips. Use blue sticky traps from the start for monitoring, irrigate adequately during dry spells, and remove crop residues after harvest.