Pigeons will be on the look out for food now, so your Brassicas; Cabbages, Cauliflower and Kale plants make suitably tasty winter meal for birds such as woodpigeons and doves. The leafy varieties like spring cabbage attract cabbage-white butterflies too that lay eggs of the underside of leaves. The resulting caterpillars that hatch then have a ready source of food – your crop!
You can prevent this attack from garden pests by providing netting- it’s a natural and organic way of keeping the pests away.
Brassicas are also victim to cabbage root flies whose maggots attack the roots in spring and summer.
This results in a poor crop of Brassicas that may wilt and die. You can nip the problem in the bud though by applying Collars to the base of young plants. The eggs simply dry up and die on this protective barrier.
Alternatively or additionally you can apply a solution containing Nematodes that is a biological means of controlling cabbage root fly and pests of other crops.