Summer is the season when pests are at their most active, because warmth and abundant soft growth give them everything they need to breed fast. A small aphid colony in June can become a large one in a week, slugs that were a nuisance in spring become a serious problem in a wet summer, and caterpillars can strip a brassica in days. The good news is that summer is also the season when predators are at their most active — ladybirds, lacewings, birds and ground beetles all eat pests — and a garden that welcomes them will have fewer problems than one that relies on sprays alone. This guide covers the main summer pests, how to recognise them, and the practical controls that work, starting with the simplest and reaching for stronger measures only when they are needed. For local advice, check your local extension service.
The summer pest mindset
The first step in summer pest control is to accept that some pests are normal, and that a garden with no pests at all is a garden with no predators either. The aim is not to eliminate every aphid but to keep numbers low enough that plants stay healthy and productive, and to act early, when a problem is small and easy to deal with. Walk the garden regularly — at least twice a week in summer — and look at the undersides of leaves, the growing tips and the soil surface, because that is where pests hide. A problem found on a Tuesday is a small job; the same problem found three weeks later is a crisis.
Prevention is worth more than cure in summer. Healthy plants grown in good soil, watered at the roots and not overfed with nitrogen, resist pests better than stressed plants. Spacing plants so air can move through them reduces disease and makes life harder for pests that like damp, still air. Removing dead leaves and spent crops promptly takes away the shelter pests hide in, and rotating crops so the same family does not grow in the same bed year after year breaks the cycle of soil pests. The pest identifier helper can help you narrow down what you are seeing before you act.
Aphids, whitefly and spider mites
Aphids are the most common summer pest, clustering on soft shoot tips and the undersides of leaves, where they suck sap and distort growth. They are also the easiest to deal with: a strong jet of water knocks most of them off, and ladybirds, lacewing larvae and hoverfly larvae eat them in large numbers. Avoid overfeeding with nitrogen, which produces the soft growth aphids love, and avoid broad sprays that kill the predators along with the pests — a garden sprayed clean of aphids is a garden with no food for ladybirds, and the aphids will return before the predators do.
Whitefly clouds up from brassicas, tomatoes and other crops when the plant is disturbed, and spider mites leave fine webbing and speckled, bronzed leaves on plants in hot, dry conditions, especially under cover and on houseplants moved outdoors. Whitefly can be reduced by hanging yellow sticky traps and by encouraging predators, while spider mites are best dealt with by raising humidity — misting plants, watering the floor of a greenhouse — and by removing the worst-affected leaves. In both cases, the first step is correct identification, because the wrong treatment wastes time and can make the problem worse.
Slugs, snails and caterpillars
Slugs and snails are at their worst in a wet summer, feeding at night on seedlings, lettuce, hostas and strawberries. Go out after dark with a torch and remove them by hand — it is the most reliable control there is — and keep beds clear of debris where they hide during the day. Barriers such as copper tape around pots, sharp grit around vulnerable plants, and beer traps sunk into the soil all help, but none of them is a complete answer on its own. Watering in the morning rather than the evening leaves the surface drier at night, when slugs are active, and that alone reduces damage.
Caterpillars are the summer pest of brassicas above all: cabbage white butterflies lay eggs on the undersides of leaves, and the caterpillars that hatch can strip a plant in days. Check the undersides of leaves weekly and remove eggs and caterpillars by hand, and cover brassicas with fine mesh from planting so the butterflies cannot lay eggs at all — this is the single most effective control. The same mesh protects carrots from carrot fly and lettuce from other pests. For crop detail, see growing tomatoes and growing lettuce, and our summer vegetable care guide.
Beetles, bugs and borers
Flea beetles riddle young brassicas and radishes with tiny holes in hot, dry summers, and the best defence is a fine mesh cover from sowing, plus keeping the soil moist so seedlings grow quickly past the vulnerable stage. Japanese beetles, where they occur, feed on roses, fruit and many other plants in midsummer; hand-picking them into soapy water in the morning, when they are sluggish, is effective for a home garden, and traps should be placed well away from the plants you want to protect, because they attract beetles from a wide area.
Squash vine borers and other borers are harder, because the damage is done inside the stem where you cannot reach it. The signs — a plant wilting suddenly despite adequate water, and a sawdust-like material at the base of the stem — mean the borer is already inside, and the best response is to cut out the affected stem, bury the stem of a healthy plant at a leaf joint so it can root, and cover the crop with mesh next year. Prevention, in the form of mesh covers and crop rotation, is worth far more than cure for borers. If you are unsure what pest you are dealing with, ask your local extension service, which can often identify a pest from a photo or a sample.
Disease in hot weather
Summer pests and summer diseases travel together, and the same habits prevent both: water at the roots rather than over the foliage, space plants for air flow, remove dead leaves promptly, and do not work among wet plants. Powdery mildew appears as a white coating on leaves in warm, dry weather, especially on squash, cucumbers and roses; improve air flow, avoid overhead watering, and remove the worst-affected leaves. Blight on tomatoes and potatoes spreads in warm, wet weather, and the first sign — dark spots on lower leaves — should prompt you to remove affected leaves and improve air circulation immediately.
Blossom end rot on tomatoes is not a disease but a watering problem: irregular watering stops the plant taking up calcium, and the end of the fruit turns dark and sunken. Keep watering even and mulch heavily, and the problem usually disappears. Do not compost diseased material — put it in the green waste bin — and clean tools between plants when you have been cutting diseased growth. Our summer watering guide and summer mulching guide cover the watering and mulching habits that prevent most summer disease.
A summer pest-control checklist
Walk the garden twice a week and look at the undersides of leaves and the growing tips. Remove pests by hand where you can, use water, traps and mesh covers before reaching for any spray, and protect predators by avoiding broad sprays. Keep plants healthy with even watering, mulch and sensible feeding, and remove dead and diseased material promptly. Note which pests appeared, when, and on which plants, because that record is the basis of next year's prevention — a mesh cover put on at planting time is worth more than any treatment applied after the damage is done.
Summer pest control is a routine, not an emergency response, and the gardeners with the fewest pest problems are usually the ones who look most often and act earliest. Build the habit of a regular walk, keep your covers and traps ready, and let the predators do as much of the work as they can. For the rest of the summer routine, read our summer watering guide and summer harvesting guide, and browse the guides hub for the full seasonal series.
Frequently asked questions
What are the most common summer garden pests?
Aphids on soft shoot tips, whitefly on brassicas and tomatoes, spider mites in hot dry conditions, slugs and snails in wet weather, and caterpillars on brassicas. Walk the garden twice a week and check the undersides of leaves, where most pests hide.
How do I get rid of aphids without spraying?
Blast them off with a strong jet of water, and encourage ladybirds, lacewings and hoverflies, which eat them. Avoid overfeeding with nitrogen, which makes soft growth aphids love, and avoid broad sprays that kill the predators as well as the pests.
How do I stop caterpillars eating my brassicas?
Cover brassicas with fine mesh from planting so cabbage white butterflies cannot lay eggs, and check the undersides of leaves weekly, removing eggs and caterpillars by hand. Mesh is the single most effective control.
What is the best slug control in summer?
Go out after dark and remove slugs by hand, keep beds clear of debris where they hide, water in the morning so the surface is drier at night, and use barriers such as copper tape or sharp grit around vulnerable plants. No single method is a complete answer on its own.
When should I use a spray on pests?
Only when cultural and physical controls have not worked, and only after identifying the pest correctly — the pest identifier helper can help. Choose the most targeted option available, apply it in the evening when pollinators are not flying, and check your local extension service for advice on what is appropriate in your area.