Physical and cultural controls that work

Barriers are the most reliable intervention. Enviromesh or insect netting (1.35 mm gauge) excludes carrot root fly, cabbage whites, flea beetle and aphids if secured at ground level with soil or pegs. It needs to go on at sowing or planting — once the pest is inside, you have trapped it with the crop. Fleece is less effective (slugs get under it) but useful for early warmth. Copper tape around pots deters slugs and snails with a mild electric shock from the mucus-metal reaction; it works but needs to stay clean and unbroken.

Timing dodges the problem. Sow carrots after late May to miss the first carrot fly generation, or under mesh from the start. Plant brassicas in July for autumn harvest when cabbage white pressure has eased. Lift potatoes before late August to avoid slug damage in wet soil. Hoe or hand-weed while weeds are tiny — waiting until they are visible from the house is waiting too long. Weeds compete for nutrients and harbour pests; remove them young.

Hand-picking is underrated. Squash aphid colonies between finger and thumb. Drop lily beetles and vine weevils into a jar of soapy water (they drop and play dead if you approach slowly, so hold the jar underneath). Pick cabbage white eggs off the undersides of leaves every few days through summer. Check brassicas for caterpillars twice a week and remove them. This sounds tedious but takes less time than you expect and gives you an excuse to look closely at your plants.

Encourage predators and accept some damage. A few nibbled leaves in May often means a clean crop by July once the hoverflies and ladybirds have multiplied. If you intervene too early or too hard, you remove the prey base and the predators leave. If you grow vulnerable plants — roses, broad beans, lettuce — assume you will share. Plant extras. Accept that perfection is not the point.