How do I deal with garden pests?

Most garden pest problems are self-limiting if you leave the predators alone. Aphid populations crash when ladybirds and hoverflies arrive; a garden sprayed with insecticide has no predators, so the next aphid outbreak is worse than the first.

What you'll need

• Hose
• Nematodes (optional)
• Horticultural soap (optional)
• Netting or fleece (optional)
• Hand lens (optional)

Step by step

1. Identify the pest before doing anything.Look under leaves and at the growing tips. Aphids cluster on soft new growth; vine weevil adults notch leaf edges; slug damage is irregular holes with slime trails.
2. Decide whether the damage actually matters.A few holes in a mature shrub's leaves affect nothing. Seedlings and crops are a different matter.
3. For aphids, blast them off with a hose or squash them by hand.Repeat every few days. Populations usually collapse once ladybirds and hoverfly larvae find them.
4. For caterpillars, pick them off and check the undersides of leaves for eggs.Netting brassicas before the butterflies arrive prevents the problem entirely.
5. For vine weevil — notched leaves and plants collapsing in pots — use nematodes.The grubs eat roots and are the real damage. Nematodes watered onto the compost are the effective control.
6. For slugs and snails, protect the vulnerable plants rather than trying to eliminate them.See the slug guide — barriers, hand collection and nematodes work; broad treatments do not.
7. Encourage predators: birds, hoverflies, ladybirds, ground beetles.A pond, flowers for pollinators, and leaving some habitat does more over time than any spray.
8. Avoid broad-spectrum insecticides.They kill predators as well as pests, so the next outbreak is worse. Reach for them last, if at all.

Tips

• A healthy, well-watered plant in the right place resists pests far better than a stressed one. Most pest problems start as growing-condition problems.
• Netting and fleece prevent damage rather than treating it, and they are the most effective control for brassicas, carrots and soft fruit.
• Check plants weekly. Catching an infestation early makes hand removal viable, which avoids treatment entirely.

Common mistakes

• Spraying before identifying — Different pests need different controls, and many treatments do nothing to the actual culprit while killing beneficial insects.
• Using broad-spectrum insecticide — It removes the predators that were keeping the pest in check, so the rebound is worse.
• Aiming for zero damage — A garden with no insects supports nothing. Some damage is the cost of a functioning garden.

Questions people ask