Tomatoes: Pests & Diseases
Tomatoes reward regular attention in British gardens, whether grown outdoors against a warm wall, in pots or under glass. Good airflow, steady moisture and prompt removal of damaged leaves are especially important in wet summers, when foliage problems can spread quickly between plants.
Common pests
Aphids gather on soft shoots and can distort growth. Glasshouse whitefly is common under cover, while red spider mite thrives in hot, dry greenhouses and causes pale speckling. Tomato moth caterpillars may bore into stems or fruit, particularly in protected crops. Slugs and snails can also graze young plants. Check imported plants carefully before bringing them into a greenhouse.
Common diseases
Tomato blight is the most serious outdoor disease, causing dark leaf patches, stem lesions and rapidly spoiling fruit; potato blight can provide a nearby source. Grey mould affects wounded or crowded plants. Leaf mould is chiefly a greenhouse problem in humid, poorly ventilated conditions. Tomato mosaic virus causes mottled, distorted foliage. Blossom end rot is a physiological disorder linked to irregular watering and calcium uptake.
Prevention
Choose blight-resistant varieties for exposed sites and avoid growing tomatoes beside potatoes where possible. Space plants so leaves dry promptly, remove lower leaves as plants develop, and water the soil rather than foliage. Ventilate greenhouses every day, keep tools and pots clean, and use fresh growing media. Maintain even watering and avoid sudden drying followed by soaking. Isolate new plants until they appear healthy.
Non-chemical control
Pick off tomato moth caterpillars and heavily infested leaves by hand. Wash small aphid colonies from sturdy shoots with water, and encourage hoverflies, lacewings and ladybirds nearby. Use fine mesh on vents where practical to reduce whitefly entry. Under glass, Encarsia can help manage whitefly and Phytoseiulus can tackle red spider mite. Remove and bin blighted foliage or fruit; do not compost diseased material.
What to look for
From planting onwards, inspect shoot tips weekly for aphids and the undersides of leaves for whitefly, mite speckling and mould. In warm, humid spells, check daily for grey mould and leaf mould. From mid-summer, look for blight after wet weather, especially on outdoor plants and nearby potatoes.
Tips
Support plants well and harvest ripe fruit often to improve airflow and reduce splitting. Water consistently, preferably in the morning. If blight appears, remove affected material promptly and pick any sound, near-ripe fruit before the disease reaches it.
Tomatoes pests & diseases: frequently asked questions
What are the common pests of tomatoes?
Aphids gather on soft shoots and can distort growth.
What diseases affect tomatoes?
Tomato blight is the most serious outdoor disease, causing dark leaf patches, stem lesions and rapidly spoiling fruit; potato blight can provide a nearby source.
How do I prevent pests and diseases on tomatoes?
Choose blight-resistant varieties for exposed sites and avoid growing tomatoes beside potatoes where possible.
General guidance for UK home gardens, focused on prevention and non-chemical control. The RHS or a local garden centre can help with tricky cases. Page updated 18 Sep 2026.