Not everything that eats your plants is a crisis. Most pests are a nuisance, not a disaster, and the worst of them are the ones your climate encourages. Below are the 20 pests and diseases we researched for Scotland: what they look like, which crops they hit, and where it exists, what actually stops them.
🐌 Molluscs
🦠 Diseases
The disease that can end a maincrop in a fortnight. Scotland’s warm, wet summers give it exactly the conditions it wants, and there is no amateur fungicide that stops it.
Affects: Potatoes
Same organism as potato blight, but it destroys the fruit rather than the tubers. Growing under cover reduces the risk, but also creates the humidity that accelerates it if spores get in.
Affects: Tomatoes
A brassica disease that contaminates soil for twenty years. Scotland’s naturally acidic, wet ground gives it ideal conditions: prevention matters more here than anywhere.
Affects: Kale, Broccoli, Cabbage, Brussels Sprouts
The permanent soil disease. Sclerotia survive fifteen years or more, there is no treatment, and the only defence is never bringing it onto your plot on tools or boots.
Affects: Onions, Garlic, Leeks, Chives
Orange pustules that thrive on wet allium leaves. No amateur fungicide exists for it, so spacing plants for airflow and keeping water off the foliage are your practical levers.
Affects: Leeks, Garlic, Onions, Chives
The fuzzy grey mould that appears on strawberries, raspberries and under cover. Its spores are always in the air: the only control is denying it the still, humid air it needs to take hold.
Affects: Strawberries, Raspberries, French Beans, Courgettes +2 more
The white dusty coating on courgette leaves that most gardeners misdiagnose. It is a dry-conditions disease: watering regularly and mulching helps more than drying things out further.
Affects: Courgettes
Not the same thing as powdery mildew despite the name. This one loves wet leaves and still air: keep foliage dry, ventilate under cover, and never water in the evening.
Affects: Spinach
Seedlings that keel over overnight with white fungal growth at the base. Hits hardest in the low light and cool temperatures of a Scottish February, exactly when most growers start seeds under cover.
Affects: Seedlings of almost anything
Orange dusty pustules on mint stems and leaves, not the same organism as leek rust. Has a unique control that works on no other disease: heat-treat rhizomes at exactly 44°C for ten minutes.
Affects: Mint
An orange-brown rot that attacks parsnip shoulders, especially where roots have already split or been damaged. Grow resistant varieties and water steadily to keep the roots from cracking.
Affects: Parsnips
🐛 Insects
The maggot that tunnels through carrot, parsnip and parsley roots underground. Insect-proof mesh is the answer; the onion-companion folklore people reach for first is not.
Affects: Carrots, Parsnips, Parsley
Sap-sucking bugs that very rarely kill plants and are a vital food source for ladybirds, hoverflies and birds. The advice is to tolerate them: the predators usually catch up by midsummer.
Affects: Tomatoes, French Beans, Peas, Lettuce +4 more
The butterflies are pretty; their caterpillars can strip a brassica bed bare. Mesh, hand-picking and encouraging wasps do the job: no chemicals needed.
Affects: Kale, Broccoli, Cabbage, Brussels Sprouts
Tiny white-winged insects that swarm up in clouds when you brush a leaf. Glasshouse whitefly thrives in the warm enclosed spaces that Scottish growers depend on for tomatoes.
Affects: Tomatoes, Basil
Adult weevils notch leaves harmlessly; their larvae eat roots from autumn to spring and kill the plant without warning. The right nematode species is the difference between control and failure in cold Scottish soil.
Affects: Strawberries
A small brown moth whose caterpillars mine allium leaves and bore into stems. It is mainly found in southern England and spreading north: probably not a Scottish problem yet.
Affects: Leeks, Onions
More common than leek moth, but still mainly recorded in England and Wales. Fine insect-proof mesh at 0.8mm stops it; standard mesh does not, so buying the wrong one wastes a season.
Affects: Leeks, Onions, Garlic, Chives
Tiny black beetles that pepper brassica seedlings with shot-hole damage. Established plants shrug them off: this is a seedling-stage problem, not something that threatens a mature crop.
Affects: Kale, Broccoli, Cabbage, Brussels Sprouts