Protecting Brassicas from Pigeons and Cabbage White Butterflies

Why brassicas need a barrier

If you grow cabbages, kale, sprouts, broccoli or cauliflower on an allotment, you will already know the heartbreak of a crop stripped overnight. Wood pigeons are the main culprits in winter and early spring, tearing at leaves with their beaks and leaving ragged stalks. From late spring onwards, cabbage white butterflies arrive to lay eggs, and their caterpillars can reduce a healthy plant to a skeleton in days. The good news is that a simple physical barrier solves both problems at once. Cover your brassicas with fine mesh or netting held well above the leaves, then check beneath it regularly for eggs and caterpillars. That single routine is the difference between a modest harvest and a full larder.

Choosing mesh and netting that works

Not all netting is equal. Standard bird netting has large holes and is worse than useless for cabbage whites, because butterflies can squeeze through or lay eggs through the gaps. Pigeons can also peck through it. Instead, choose a fine mesh with holes no bigger than 5–7mm. Butterfly netting, insect mesh, or fine woven horticultural fleece all work well. The mesh should be strong enough to stay taut and UV-stabilised so it lasts more than one season. Avoid cheap, flimsy netting that sags and tears. For a typical allotment bed, buy enough width to drape over hoops and reach the ground on both sides. You will also need ground pegs, bricks, or lengths of timber to weigh down the edges. Any gap is an invitation.

• Fine mesh: 5–7mm holes, UV-stabilised, strong enough to stay taut.
• Ground pegs or weights: to seal the edges completely.
• Hoops or a frame: to keep the cover well above the leaves.

Holding the cover above the leaves

The most important rule is that the mesh must not touch the leaves. Cabbage white butterflies can lay eggs through netting if the leaves press against it. Pigeons can also peck through fabric that is lying directly on the foliage. Build a simple frame using blue water pipe, flexible canes, or metal hoops. Push the ends into the soil at intervals of about 1–1.5 metres, then drape the mesh over the top. For taller brassicas like Brussels sprouts or winter kale, use taller hoops or a timber frame so the cover sits at least 30cm above the mature plants. Secure the mesh to the ground with pegs every 50cm, and gather it neatly at the ends. A taut cover that cannot flap in the wind is much more effective and lasts longer.

Checking beneath the fabric

Even the best mesh is not a substitute for vigilance. Check beneath the cover at least twice a week from spring to early autumn, and daily in warm weather when butterflies are most active. Look on the undersides of leaves, along the stems, and in the growing points. Cabbage white eggs are small, yellow-orange, and laid in clusters or singly, depending on the species. The caterpillars are green, velvety, and often well camouflaged. Squash any eggs you find and pick off caterpillars by hand. If you spot small holes in the leaves, inspect immediately. A few minutes of checking saves hours of heartache later.

Watering, feeding and air flow

Covered crops still need care. Mesh reduces airflow slightly, so water in the morning rather than the evening to let foliage dry. Lift the netting at one end to water, feed, and weed, then secure it again. Brassicas are hungry plants; a liquid feed every fortnight keeps them growing strongly. Strong plants recover better from minor pest damage. Watch for slugs and snails under the edges, and remove any yellowing leaves that could harbour pests. In hot spells, shade can be useful, but most fine mesh lets enough light through. If you are using fleece, remove it once the risk of hard frost has passed.

Making protection a habit

The best protection is a routine. Plant your brassicas in firm, fertile soil and net them immediately after planting, before pests find them. Rotate your crops each year to avoid clubroot and other soil-borne problems. Companion planting with nasturtiums, marigolds, or strong-smelling herbs may help confuse pests, but never rely on it alone. In autumn, keep winter brassicas covered against pigeons, and check for caterpillars after any warm spell. At harvest, uncover only what you need, then replace the mesh. With a fine mesh cover held above the leaves and a regular check beneath it, you can enjoy clean, healthy cabbages, kale, and sprouts — and leave the pigeons and butterflies to find their dinner elsewhere.