Whitefly Control

Symptoms

Tiny white moth like insects fly up in a cloud when the plant is disturbed and settle on the underside of leaves. The nymphs and adults suck sap, causing leaves to yellow, curl and dry. They excrete sticky honeydew on which black sooty mould grows, blackening leaves and reducing photosynthesis. Most importantly, whiteflies carry and spread the deadly leaf curl virus, so even small numbers are a serious threat.

Damage

Whitefly Bemisia tabaci damages crops in two ways, by sucking sap directly and by spreading leaf curl virus, and the virus spread usually causes far greater loss than the feeding itself. A small whitefly population can infect a whole field with virus, leading to 30 to 100 percent losses. Sooty mould on honeydew further reduces fruit quality. Because it breeds fast and develops insecticide resistance quickly, whitefly is one of the hardest pests to manage in solanaceous crops.

Organic & cultural control

Use yellow sticky traps at 10 to 12 per acre as whiteflies are strongly attracted to yellow, both to monitor and to trap them. Raise nurseries under insect proof nets. Spray neem oil at 5 ml per litre or neem seed kernel extract at 5 percent which repels whiteflies and checks nymphs, and add a sticker for better coverage on the leaf underside. Verticillium lecanii bio insecticide controls whitefly in humid conditions. Use reflective silver mulch to confuse whiteflies and remove weed hosts around the field.

Chemical control

When whitefly numbers rise, use insecticides such as diafenthiuron 50 WP, pyriproxyfen, spiromesifen, flonicamid or a neonicotinoid like imidacloprid or thiamethoxam, spraying thoroughly on the underside of leaves. Rotate insecticide groups strictly because whitefly develops resistance very fast and many products have already lost effect. Avoid repeated use of the same neonicotinoid. Always follow the product label dose, observe 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

Grow tolerant varieties, use insect proof nurseries and transplant only healthy whitefly free seedlings. Keep yellow sticky traps from the start, remove weeds and old infected crop debris, and follow a crop free period to break the breeding cycle. Avoid planting next to cotton, brinjal or older tomato crops that harbour whitefly. Avoid excess nitrogen which makes plants soft and attractive, and do not overuse broad spectrum insecticides that kill the natural enemies of whitefly.