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Brassica Pests & Problems

Club Root - Plasmodiophora Brassicae

This is one of the worst problems for the gardener to cope with, but the good news is that it can be coped with and new resistant varieties are making life much easier. See Coping with Clubroot for more information

Cabbage Root Fly

Another serious pest of the brassica family but it can be prevented from causing damage by barrier methods. See The Cabbage Root Fly for more information.

Butterflies & Caterpillars

The butterflies are not actually a problem but their caterpillars are. Eggs are laid, usually under the leaf, which hatch out the caterpillars that eat the crop. Worst affected are cabbages and cauliflowers but all leaf brassicas can suffer.

They are fairly easy to control without resorting to chemicals or biological controls. Regularly check under the leaves for clusters of eggs. These will be seen as small (approximately 2mm) yellow or white spheres. Just wash them off or crush them with your finger.

If you miss a batch then you can pick off the caterpillars by hand and dispose of them away from the plant. It is no more work than spraying the caterpillars with a chemical (Derris) or a nematode based biological control.

Flea Beetle

This pest is worst on radishes but can affect turnips and swedes as well. It is a small beetle that jumps when disturbed, hence the name 'flea beetle' The beetle eats holes in the leaves which weaken the plant as with less leaf area to produce food for the plant it cannot grow as well.

You can spray with a pesticide such as Derris. The active ingredient is rotenone which is made from tropical plant extracts. It is organically approved but you could try an alternative strategy from Bob Flowerdew. Coat one side of a piece of cardboard with treacle and wave the card just above the affected plant, brushing the topmost edges of the leaves. The beetle jumps onto the treacle and sticks there. The card can then be fed to chickens who will pick off the flea beetles. Even if you do not have chickens, still worth it to avoid using an insecticide.

Cabbage Whitefly

These small white flies suck the sap of the plant through the leaves. Great clouds of them may fly up when the leaves are disturbed. They don't cause too much harm and are easily handles by either washing with a jet of water, insecticidal soap or derris.

Insecticidal soap does not contain an insecticide as such, just fatty acids that block the breathing holes of the pest.

Mealy Aphids

These are grey-green aphids that form colonies on the leaves and stems in the summer. They can cause a serious check to growth and need to be addressed. Ladybirds will eat the mealy aphids or you can squash them by hand or treat with derris or insecticidal soap. They over-winter on brassica stumps so do not leave these in the ground after harvest.

Pigeons & Birds

Pigeons are serious pest, especially in winter when their food sources are scarce. The only real answer is to net the crop to stop them from getting to the leaves. Do ensure the net is supported so that the weight of the pigeon cannot bend it onto the leaves and allow it to feed.

You can buy various bird scarers or make your own. I have seen pigeons sitting on CDs placed as a bird scarer and they have taken a tray of seedlings from our garden where three, admittedly elderly, cats live. Nests are the only answer I know that works.