The right netting, put up at the right time, is the single most effective way to keep cabbage white caterpillars off your brassicas — here's what mesh size and setup actually work.
Last updated 6 July 2026
Growing kohlrabi this year? Our full guide to growing kohlrabi in the UK covers sowing, spacing and harvesting alongside the pest protection below.
Every brassica in a UK vegetable garden — kohlrabi, cabbage, kale, sprouts and the rest — is a target for cabbage white butterfly caterpillars from late spring onward. Sprays and hand-picking help, but netting put up before the butterflies find your plants is by far the most reliable defence. Here's what actually works.
Mesh Size Matters
Fine insect mesh (around 4–7mm) excludes cabbage white butterflies completely and also helps against flea beetle on young seedlings. Standard brassica netting with a wider mesh (around 25mm) is cheaper and still stops butterflies, which are too large to pass through, but won't do anything against smaller pests. For a bed of mixed brassicas, fine mesh is worth the extra cost.
Timing: Net Before You See a Problem
The most common mistake is netting reactively, after caterpillars are already spotted. By the time damage is visible, eggs or young caterpillars are usually already established under the leaves where netting can't reach them. Net at the point of sowing or transplanting, and keep it in place continuously through summer — our guide to protecting brassicas from cabbage white butterfly covers the full seasonal timeline and what to do if you're netting late.
Getting the Setup Right
Netting only works if it's properly secured and held clear of the leaves:
- Use hoops or a simple frame to keep netting off the foliage — butterflies can lay eggs through netting that's resting directly on leaves.
- Bury or peg the edges firmly into the soil all the way around; a gap of even a few centimetres is enough for a butterfly to find its way in.
- Check under the netting every week or two and remove any caterpillars or eggs that get through, since no barrier is completely perfect.
Reusable woven mesh lasts for years if stored dry over winter and is generally better value than lightweight single-season netting, especially if you're protecting several brassica beds at once.
Plan Your Entire Growing Season
Month-by-month sowing schedules, crop guides for every UK vegetable, companion planting charts, and harvest trackers — all calibrated for UK conditions.
Get the UK Garden Planner →Frequently Asked Questions
What mesh size stops cabbage white butterflies?
Standard 25mm brassica netting is enough to stop butterflies, which can't fit through. Finer 4–7mm insect mesh does the same job while also excluding flea beetle, making it the better choice if you're protecting young seedlings too.
When should I net my brassicas?
From the moment you sow or transplant, not after you spot caterpillar damage. Eggs and young caterpillars are usually already established under leaves by the time damage becomes visible, so netting works best as prevention rather than a reactive fix.
Can butterflies lay eggs through netting?
Yes, if the netting is resting directly on the leaves. Use hoops or a frame to hold netting clear of the foliage, and peg or bury the edges so there are no gaps at ground level.
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