Common vegetable pests & diseases: spot and prevent
Most kitchen-garden problems are easier to prevent than to cure. Learning to recognise the common pests and diseases early, and giving plants the airflow, spacing and healthy soil they need, keeps damage small and the harvest coming.
Common pests
These are the pests you are most likely to meet. Check shoot tips, leaf undersides and soil level, where most of them hide and feed.
| Problem | What you see | First response |
|---|---|---|
| Aphids | Clusters of tiny green, black or grey insects on shoot tips, sticky honeydew and curling leaves | Rinse off with a jet of water; encourage ladybirds, lacewings and hoverflies |
| Whitefly | Tiny white flies that rise in a cloud when leaves are disturbed, sticky residue underneath | Hang yellow sticky traps; improve ventilation; introduce natural predators |
| Spider mite | Fine pale speckling on leaves, faint webbing beneath, foliage bronzing in dry heat | Raise humidity and mist plants; remove the worst leaves; avoid drought stress |
| Cabbage white caterpillars | Ragged holes in brassica leaves, green or velvety caterpillars and yellow egg clusters underneath | Cover crops with insect-proof mesh; pick off caterpillars and eggs by hand |
| Slugs & snails | Irregular holes with slime trails, seedlings grazed to the ground overnight | Clear hiding places; water in the morning; use barriers, traps or nematodes |
| Flea beetle | Many tiny shot-hole pinpricks on rocket, radish and brassica leaves, beetles that jump when disturbed | Protect seedlings with mesh; keep soil moist; grow crops on quickly |
| Carrot fly | Rusty tunnels in carrot, parsnip and celery roots, reddish wilting foliage | Sow thinly to avoid thinning; use a fine mesh barrier or fleece |
Common diseases
Most vegetable diseases take hold in damp, still, crowded conditions. Spot them early and the response is usually about airflow and hygiene, not spraying.
| Problem | What you see | First response |
|---|---|---|
| Powdery mildew | White powdery patches on leaves and stems, often in dry soil with humid air | Improve airflow and spacing; water at the base; remove affected leaves |
| Late blight (tomato/potato) | Brown blotches on leaves, dark stem lesions and rapidly rotting fruit or tubers in warm, wet spells | Space for airflow, water at the base; remove and bin affected plants promptly |
| Downy mildew | Yellow patches on the upper leaf with grey or purple mould beneath | Increase spacing and ventilation; avoid wetting foliage; rotate crops |
| Damping-off | Seedlings collapse at soil level and topple over soon after germinating | Use clean trays and fresh compost; sow thinly; avoid overwatering |
| Grey mould (botrytis) | Fuzzy grey-brown mould on stems, leaves and fruit in cool, damp conditions | Remove affected parts; improve ventilation; avoid overhead watering |
| Rust | Orange, brown or yellow pustules on leaves of leek, garlic, beans and chard | Remove infected leaves; space plants; rotate crops and avoid excess nitrogen |
Prevention first
Strong, unstressed plants shrug off most trouble. Give each crop enough space for air to move between the leaves, water at the base in the morning rather than over the foliage, and feed the soil with compost so roots stay healthy.
Rotate crops so pests and diseases cannot build up in one spot, mix in flowers and herbs to draw in pollinators and natural predators, and check plants regularly so you catch problems while they are still small and local.
Confirm before you treat
This is general guidance, not a diagnosis. Symptoms often overlap — nutrient shortages, weather stress and watering mistakes can all mimic pests and diseases — so confirm what you are dealing with before acting, and always start with the gentlest cultural fix.
If you are unsure, aimanac's photo diagnosis can help identify the issue from a photo of the affected plant and suggest sensible next steps.