Spring is when pests wake up, and the first ones arrive just as the garden's soft new growth appears. Aphids cluster on the tender tips of roses and broad beans, slugs eat seedlings overnight, cutworms sever young stems at soil level, and the first fungal diseases appear on leaves that stay wet in cool spring weather. The gardener who spots these problems early, in spring, can control them with simple measures; the gardener who notices them in summer is often too late. This guide covers the first pests and diseases of spring, how to spot them, and how to deal with them while protecting pollinators and beneficial insects.
The first pests of spring
Aphids are the classic spring pest. They appear as soon as soft new growth emerges, clustering on shoot tips, buds and the undersides of young leaves, and they multiply fast in warm spring weather. They suck sap, distort growth, and spread viruses, and their sticky honeydew attracts ants and sooty mould. Check shoot tips weekly from early spring, especially on roses, broad beans, fruit trees and lettuce. A strong jet of water dislodges a light infestation, and encouraging ladybirds, lacewings and hoverflies — which all eat aphids — is the best long-term control. Avoid broad-spectrum insecticides in spring, because they kill the predators as well as the aphids, and the aphids come back faster.
Slugs and snails are the second spring pest, and they do their damage at night, eating seedlings, hostas and young lettuce down to the stem. Look for silvery trails and ragged holes in leaves, and check under pots and boards in the morning. The best spring control is cultural: clear debris where slugs hide, water in the morning so the soil surface dries by night, and protect seedlings with copper tape, grit barriers or beer traps. Go out with a torch on a damp evening and pick slugs off by hand — it is unglamorous and it works. Use slug pellets only as a last resort, and choose ones that are safe for wildlife if you do. Check your local extension service for pest identification help if you are unsure what is eating your plants.
Cutworms, flea beetles and other early pests
Cutworms are caterpillars that live in the soil and cut young seedlings off at the base overnight. A seedling that is healthy one evening and lying flat the next morning has probably been cut by a cutworm. Protect seedlings with a cardboard collar pushed an inch into the soil around the stem, and dig over beds before planting to expose the caterpillars to birds. Flea beetles make small holes in the leaves of brassicas and radishes in spring, and they are worst in hot, dry weather — keep the soil moist and cover young brassicas with fleece to keep the beetles off.
Vine weevils become active in spring, and their grubs eat the roots of container plants. Carrot fly appears in late spring and lays eggs at the base of carrots; cover carrots with fleece from sowing to keep the flies off. Whitefly appears on plants under glass and on brassicas in mild springs. In all cases, the spring principle is the same: inspect weekly, catch the problem early, use physical barriers and hand-picking first, and use a spray only when the problem is beyond those measures. The pest identifier helper can help you work out what you are looking at.
The first diseases of spring
Spring diseases are mostly fungal, and they thrive in the cool, wet conditions of spring. Damping off kills seedlings in damp, still air — see our spring seed starting guide for prevention. Powdery mildew appears as a white powder on leaves in dry, warm spells. Early blight and other leaf spots appear on tomatoes and potatoes as the weather warms. Rust appears as orange spots on the undersides of leaves on roses, hollyhocks and beans. The common factor is wet leaves and poor air movement, so the best spring disease control is to water the soil rather than the leaves, space plants so air moves between them, and remove infected leaves promptly.
Remove and dispose of diseased material — do not compost it, because home compost does not get hot enough to kill fungal spores. Clean tools between plants when you have been cutting diseased growth, and do not work among wet plants, because you spread spores on your hands and clothes. Choose resistant varieties where you can, and rotate crops so the same family does not grow in the same bed year after year. If a disease keeps recurring, check your local extension service for diagnosis and for varieties that resist it in your area.
Protecting pollinators and beneficial insects
Spring is when pollinators emerge, and the garden needs them: bees, hoverflies and other pollinators are essential for fruit and vegetables, and many of them are also pest predators. The most important rule of spring pest control is to protect them. Never spray a flowering plant, never spray in the middle of the day when bees are active, and never use a broad-spectrum insecticide when a targeted measure would do. If you must spray, do it in the evening, when bees have gone home, and use a product that is labelled as safe for bees and that targets the pest you have.
Encourage beneficial insects by planting flowers that feed them: early flowers such as crocus, primrose and pulmonaria feed bees in early spring, and later flowers such as calendula, borage and phacelia feed hoverflies and lacewings all season. Leave a small wild corner, a log pile or a patch of long grass for predators to shelter in, and avoid tidying the whole garden at once in spring — many beneficial insects overwinter in dead stems and leaf litter, and clearing everything destroys them. Our spring garden cleanup guide explains how to tidy without destroying wildlife habitat.
A spring pest watch routine
Walk the garden once a week in spring, looking at shoot tips, the undersides of leaves, and the soil surface around seedlings. Look for clusters of small insects, ragged holes, silvery trails, wilting seedlings, and spots or powder on leaves. Catching a problem in its first week means a jet of water or hand-picking is enough; catching it in its fourth week means the plant may be lost. Keep a note of what you find and when, because the same pests return at the same time each year, and next spring you will know what to watch for. If a pest or disease defeats you, check your local extension service — a photo and a description will usually get you an identification and a control plan.
Frequently asked questions
What pests appear first in spring?
Aphids on soft new growth, slugs and snails on seedlings, cutworms on young stems, and flea beetles on brassicas. Inspect shoot tips and seedlings weekly from early spring.
How do I control aphids without chemicals?
A strong jet of water dislodges them, and encouraging ladybirds, lacewings and hoverflies gives long-term control. Avoid broad-spectrum sprays, which kill the predators too.
What is eating my seedlings overnight?
Probably slugs or cutworms. Look for silvery trails for slugs, and for stems cut cleanly at soil level for cutworms. Use barriers, hand-picking and cardboard collars.
How do I prevent spring fungal diseases?
Water the soil, not the leaves, space plants for airflow, remove infected leaves promptly, and do not compost diseased material. Choose resistant varieties where you can.
When should I spray for pests in spring?
Only when hand-picking, water and barriers have failed, and then in the evening when bees are not active, using a targeted product. If you are unsure, check your local extension service for advice.