Aphids
Soft-bodied sap-suckers that curl and stunt tender growth, coat it in sticky honeydew — and spread viruses as they feed.
- Pest type
- Sap-sucking insect
- Attacks
- Shoots, leaf undersides
- Worst in
- Cool, dry weather
- Main risk
- Virus spread + honeydew
Overview
Aphids are small, soft, pear-shaped insects — green, black, brown or grey — that live in dense colonies on the growing tips, flower stalks and the undersides of young leaves. They pierce the plant and suck sap, so leaves curl, crinkle and yellow and growth slows.
The bigger loss is often indirect. Aphids excrete sticky "honeydew" that a black sooty mould grows on, cutting photosynthesis, and several aphid species carry plant viruses from plant to plant — a mustard or potato crop can lose more to aphid-borne virus than to the feeding itself. Because they breed explosively in cool, dry weather, a small colony becomes a crop-wide problem in days.
How to identify it
- Dense clusters of small (1–3 mm) soft-bodied insects on the youngest shoots, buds and the underside of tender leaves.
- Colonies are green, black, grey or brown; a pair of tiny "tailpipes" (cornicles) at the rear tell aphids from other sap-suckers.
- Winged forms appear when a colony gets crowded — that is when they fly off and spread virus to fresh plants.
- Ants running up and down the plant are a giveaway — they farm aphids for their honeydew.
The damage it does
- Leaves curl, crinkle, yellow and distort; shoots and flower stalks are stunted and twisted.
- A sticky honeydew coating turns black with sooty mould, blackening leaves and fruit and cutting photosynthesis.
- Virus transmission — leaf curl, mosaics and yellows — which often costs more than the direct feeding, especially in mustard, potato, chilli and cucurbits.
- In mustard, heavy late-season colonies on the pods can shrivel the seed and slash oil yield.
When to act
- Scout the crop twice a week from early growth, checking the undersides of the top few leaves and the growing tips.
- Act early — aphids are easiest and cheapest to stop while colonies are small and before winged forms spread virus.
- Do not spray at the first aphid if ladybird beetles, lacewings and hoverfly maggots are present in numbers; they often crash a colony on their own.
Organic & cultural control
- Conserve and encourage natural enemies — ladybird beetles, lacewings, hoverflies and parasitic wasps are the main check on aphids; avoid broad-spectrum sprays that kill them.
- Spray neem oil / neem seed kernel extract (NSKE 5%), which repels and stunts aphids and is soft on their predators.
- A strong jet of water, or a soap/ash solution, knocks colonies off small plots; yellow sticky traps catch the winged migrants and warn you they have arrived.
- Avoid excess nitrogen — lush, soft growth is exactly what aphids multiply on.
Chemical control
- Use a chemical only when colonies keep building despite natural enemies, and rotate insecticide groups so aphids do not build resistance.
- CIB&RC-registered options for aphids include flonicamid 50% WG, imidacloprid 17.8% SL, thiamethoxam 25% WG and acetamiprid 20% SP — choose one registered for your crop and follow the label dose.
- Spray to wet the undersides of leaves where aphids sit, and observe the pre-harvest interval on the label, especially on vegetables and fruit picked frequently.
- Confirm the current recommendation and dose for your crop and zone with your local KVK before spraying.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
Why are my leaves sticky and turning black?
That is honeydew — the sugary waste aphids excrete — with a black sooty mould growing on it. The mould itself does not infect the plant, but it blocks light and signals a heavy aphid (or whitefly/mealybug) colony above. Control the aphids and the stickiness and blackening stop.
Do I need to spray as soon as I see aphids?
Usually not. If ladybird beetles, lacewings or hoverfly maggots are present, they often bring a colony down on their own, and spraying would kill them too. Scout twice a week, use neem early, and reserve a registered insecticide for when colonies keep building despite the natural enemies.
How do aphids spread viruses?
Winged aphids pick up a virus while feeding on an infected plant and inject it into the next plant they probe. This is why early control matters more than the feeding damage suggests — a light aphid population can still seed a damaging virus outbreak in mustard, potato, chilli or cucurbits. Yellow sticky traps help you catch the migrants early.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.