Common vegetable pests and how to identify them

Watch on Broad beans, brassicas, tomatoes, courgettes and most soft new growth

Aphids are soft-bodied insects a few millimetres long, green, black, grey or pink. They gather in dense colonies on shoot tips, flower buds and the undersides of young leaves. They feed on sap, pass viruses between plants, and coat the leaves below in sticky honeydew that grows black sooty mould. New growth puckers and curls. Most colonies wash off under a hard jet of water or squash between finger and thumb, and ladybirds and hoverfly larvae often reduce the rest.

Watch on Tomatoes, cucumbers, cabbage, kale and sprouts

Whitefly are tiny white insects about two millimetres long. They shelter on the undersides of the youngest leaves and rise in a cloud when the plant is knocked, then settle again. The flat translucent scales stuck to the leaf are the young, and they do not move. Like aphids they leave honeydew and sooty mould, so lower leaves yellow and the crop weakens over a season. Kale and sprouts can carry them through winter, and the sooty deposits make leaves unpleasant to prepare.

Watch on Tomatoes, cucumbers, aubergines, beans and strawberries

Red spider mite does most harm in hot dry air, especially under glass and on tomatoes, cucumbers, beans and aubergines. The first sign is fine pale speckling across the upper leaf, like dust that will not wipe away. As colonies build, whole leaves turn dull, then bronze, then drop, and fine silk webbing appears between the shoot tips. The mites are tiny pale specks on the leaf underside that move when watched for a few seconds. Raising humidity and washing the plants slows them.

Watch on Onions, leeks, peppers, cucumbers and tomatoes

Thrips are slender insects about a millimetre long, dark brown or pale yellow. They rasp the surface of leaves and petals and feed from the damaged cells. The damage shows as silvery or bleached flecking, often with tiny black dots of excrement. New leaves come through puckered and scarred, and flower buds open badly. Thrips run rather than fly when disturbed, and hide in the crevices of unfurling growth.

Watch on Lettuce, endive, globe artichoke and container plants

Root aphids feed unseen on roots, so the plant may wilt in afternoon sun and recover overnight until one day it stops recovering. Nothing on the leaves explains the wilting. Knock the plant out of its pot or lift it, and look for small grey, yellow or cream aphids clustered on the roots and crown, often under a white or bluish waxy powder. Ants often tend them for honeydew. Lettuce, endive and globe artichoke suffer most.

Watch on Rocket, radish, turnip and brassica seedlings

Flea beetles are tiny dark beetles that jump when a hand passes over them. They pepper the leaves of rocket, radish, turnip and brassica seedlings with dozens of small round holes and shallow pits. Some pits go only part way through and leave a translucent window. A heavy attack can check or kill a young row within a week, and they are worst in warm dry spells on slow seedlings. Water well and cover with fine mesh until the plants are larger.

Watch on Potatoes, aubergines and tomatoes

Colorado potato beetle can strip a potato plant to bare midribs within a fortnight. The adult is 10 mm long, with black and cream stripes down the wing cases and an orange-red head spotted with black. Its grubs are humpbacked and orange-red, with two rows of black dots along each side. They cluster on leaf undersides beside batches of upright yellow-orange eggs. It also feeds on aubergine and tomato. Where it is established, hand-picking beetles, grubs and eggs is the main control. Report a suspected sighting in Britain, Australia or New Zealand.

Watch on Cucumbers, melons, watermelon and squash

Cucumber beetle is a small yellow beetle, 5 to 7 mm long, either black-striped or spotted. It chews the cotyledons and flowers of young cucumbers, melons and squash. The feeding matters less than the bacterium it can spread, which blocks the vine water channels and makes the plant wilt from the tip inward over a week or two. The plant does not recover overnight. Cut a wilted stem and a milky sap strings out from it. This is an American pest, so cover seedlings from the day they emerge where it occurs.

Watch on French, runner, butter and soya beans

Mexican bean beetle is a coppery-yellow relative of the ladybird, 6 to 8 mm long and domed, with sixteen black spots in three rows across the wing cases. Unlike the ladybirds it resembles, it eats bean leaves rather than aphids. Adults and spiny pale-yellow grubs feed together from the leaf underside. They skeletonise leaves between the veins and scar the pods. It is confined to the Americas and is worst in the Mid-Atlantic and Appalachian United States.

Watch on Cabbage, broccoli, kale and other brassicas

Harlequin bug is a boldly patterned shield bug about a centimetre long, marked in black with red and orange. It feeds on cabbage, kale, broccoli and other brassicas, leaving irregular white or pale cloverleaf-shaped blotches that spread into large dead patches. A heavy attack can wilt and blacken young seedlings, since they have less tissue to lose. It feeds mostly on brassicas and belongs to the southern and central United States rather than the wider world.

Watch on Cabbage, kale, sprouts, broccoli and lettuce

Caterpillars chew ragged holes through the middle and edges of leaves and drop dark frass pellets as they feed. They often hide on the leaf underside by day. On brassicas, cabbage white caterpillars can reduce cabbage or kale leaves to lace and bore into the heart. Yellow-and-black caterpillars feeding in groups are large whites; lone green ones are small whites. To separate any caterpillar from a sawfly grub, count the fleshy prolegs, since a sawfly has more pairs. Squash the yellow egg clusters and net the bed before the butterflies lay.

Watch on Cabbage, cauliflower, broccoli and Asian greens

Diamondback moth is a small grey-brown moth whose green caterpillars pepper brassica leaves with pinholes and leave translucent windowpanes where they graze the underside. Poke a leaf and the caterpillar wriggles backward and drops off on a silk thread. It is the most damaging insect pest of brassicas worldwide, and it has evolved resistance to many insecticides. Netting, predators and crop hygiene matter most.

Watch on Sweetcorn, tomatoes and peppers

Corn earworm works down through the silks and feeds inside the tip of a sweetcorn cob. By the time damage shows, the caterpillar is hidden from any spray. It also bores single holes into green tomatoes and peppers, which is why it is also called tomato fruitworm. The caterpillars range from pale green through pink to nearly black, all with fine pale stripes down the body. It is an Americas pest; an identical-looking relative, the Old World bollworm, fills the same role elsewhere.

Watch on Tomatoes, aubergines, peppers and potatoes

Tomato hornworm is a green caterpillar up to 10 cm long, with white diagonal stripes and a curved horn at the tail. It is hard to see against tomato stems, and it can strip whole branches of tomato, chilli or aubergine overnight. Dark pellet-shaped droppings on the leaves and soil are often the first sign. Leave any hornworm carrying rows of white cocoons on its back, because it has been parasitised and will do no more harm. It belongs to North and South America.

Watch on Lettuce, brassicas, beetroot, onions and sweetcorn

Cutworms are fat soft caterpillars, grey, brown or greenish, that live in the top few centimetres of soil and feed at night. They cut through young lettuce, brassicas, beet and sweetcorn stems at ground level, so a row can topple overnight with the severed tops left beside the stumps. Scratch the soil near a cut plant and you may find the caterpillar curled into a C. Older plants may have ringed or gnawed stems rather than being cut down. Hoe to expose cutworms and fit stem collars.

Watch on Carrots, parsnips and parsley

Carrot fly is often noticed only when you lift or cut the crop and find rust-brown tunnels through the outer flesh of carrots, parsnips and parsley. Above ground, the first hint is a bronze or reddish cast to the foliage, which later yellows. The low-flying adult finds the row by scent, especially when you thin or brush the leaves. Sow thinly to avoid thinning, and screen the bed with fine mesh or a low vertical barrier the flies will not climb over.

Watch on Brassica transplants, radish, swede and turnip

Cabbage root fly can make newly planted brassicas wilt within a week and die. White legless maggots up to 9 mm long eat the fine roots and tunnel the tap root, so the plant turns blue or purple, stops growing and pulls straight out of the ground with little root left. Radishes, swedes and turnips can come up riddled with brown tunnels. Transplants are most at risk. Fit a disc of card or felt tight around each stem at planting, or cover the bed with mesh from day one.

Watch on Potatoes, carrots, beetroot and seedlings

Wireworms are the thin, stiff, orange-brown grubs of click beetles, up to 25 mm long with three tiny pairs of legs at the front. They bore clean round tunnels into potatoes and up through carrots, beetroot and seedling stems. A transplant with its stem chewed below ground wilts and dies alone in the row. Wireworms are worst in the first three or four years after old turf is dug up and fade as the ground is worked. Lift maincrop potatoes promptly and fork the plot over to expose them.

Watch on Seedlings, brassicas and root crops

Leatherjackets are the legless grubs of crane flies, greyish-brown and tough-skinned, up to 4 cm long with no obvious head. They chew through roots and stem bases in the top few centimetres of soil, thinning seedbeds and leaving bare patches. On lawns, damaged turf may lift easily while birds and badgers pull it up to reach the grubs. They are most common on ground that was grass the year before. Fork the bed through before sowing and firm new transplants in well so the grubs cannot pull them under.

Watch on Tomatoes, cucumbers, carrots, potatoes and okra

Root-knot nematodes are microscopic worms that feed inside roots and swell them into rows of beads and knotted galls. The plant above ground stunts, yellows and wilts in heat however much you water it, because the damaged roots can no longer take up enough water. Lift a failing plant and the galls are clear: they are swellings that are part of the root rather than pests stuck to it. They persist in warm soil, build up wherever the same crop returns, and hit tomatoes, cucumbers, carrots and potatoes hardest.

Watch on Courgettes, pumpkins and winter squash

Squash vine borer can collapse a healthy courgette or squash within a day or two, often starting with a single runner. Look at the base of the wilted stem for a hole packed with moist, sawdust-like orange-green frass. Slit the stem there and you may find a cream caterpillar up to 2.5 cm long hollowing it out. Courgettes and pumpkins suffer far more than butternut squash growing alongside. It is an American moth, so a wilting vine elsewhere is more likely to be drought, verticillium wilt or another cause.

Watch on Seedlings, lettuce, hostas, beans and potatoes

Slugs and snails feed after dark and in wet weather, rasping smooth-edged holes in soft leaves and cutting seedlings off at the stem. By morning the plants may be gone, with only silvery slime trails across the soil and pots left behind. They can clear a row of lettuce, a hosta or a tray of seedlings overnight, and they graze craters into potato tubers below ground. Most species do little harm; grey field slug, keeled slugs and garden snail are the main ones to guard young plants against.

Watch on Cabbage, sprouts, kale, peas and beans

Wood pigeons strip leaves from cabbages, sprouts and kale until only thick midribs and stalks are left, especially in daylight through the coldest months when other food is scarce. Torn ragged edges and grey-white droppings on the plants separate the damage from caterpillars and slugs. They also pull up rows of pea and bean seedlings and strip buds and blossom from fruit. Taut netting held clear of the crop, or a fruit cage, is the only reliable defence. In other regions, other pigeons and parrots can cause similar damage.

Watch on Lettuce, beans, hostas, tulips and young trees

Rabbits and deer can clear rows of vegetables and young shoots overnight, and the cut on the stem helps tell them apart. Rabbits bite through cleanly at a sharp angle and browse up to about 50 cm. Deer tear shoots off, leaving a ragged frayed end, and reach 1.2 m or more. Both gnaw bark from young trees in winter, and deer can also shred stems by rubbing their antlers on them. Round droppings and hoof slots in soft ground confirm the cause. A fence of the right height, sunk against rabbits, keeps them out.