Aphids Control

Symptoms

Soft bodied green, black or grey aphids cluster in colonies on tender shoots, the underside of leaves, flower stalks and pods. They suck sap so leaves curl, crinkle and turn yellow, and shoots become stunted. They secrete sticky honeydew on which black sooty mould grows, blackening the leaves, and ants are often seen moving among them.

Damage

Aphids are widespread sap sucking pests of peas, beans, cole crops, okra and cucurbits, building up fast in cool to mild weather. Direct sap loss stunts plants, while honeydew and sooty mould reduce photosynthesis and spoil produce. Importantly, aphids also transmit several plant viruses, which can cause more damage than the feeding itself.

Organic & cultural control

Conserve and encourage natural enemies such as ladybird beetles, lacewings and syrphid flies which feed heavily on aphids. Use yellow sticky traps to monitor, and spray neem oil or neem seed kernel extract which checks soft aphids well. A strong jet of water can dislodge colonies on sturdy plants. Avoid excess nitrogen which produces soft growth aphids prefer.

Chemical control

When colonies are dense and natural enemies are not enough, a recommended insecticide such as dimethoate, thiamethoxam, imidacloprid or flonicamid can be sprayed, directing it to the underside of leaves where aphids hide. Rotate groups and avoid spraying during flowering to protect pollinators. Use only labelled products at the correct dose, 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

Scout regularly, especially the underside of young leaves and shoot tips, and act while colonies are small. Use balanced fertiliser and avoid excess nitrogen, and keep fields free of aphid hosting weeds. Encourage natural enemies by avoiding unnecessary broad spectrum sprays, and use yellow sticky traps and reflective mulch where practical.