Cabbage Pests & Diseases Cabbages and other brassicas have become a very important part of the vegetable garden in our climate. Different varieties of cabbages have been bred for productivity, size, and flavour over the years. However they are still quite vulnerable to pests and diseases. There are a number of pests and diseases you need to look out for and plan against when planting brassicas.
Birds & Butterflies
Shortly after sowing cabbage seeds, birds and butterflies can become a problem. Some fine bird protection netting will keep any birds away from planted seeds and later on away from growing cabbages. Bird netting will also prevent butterflies from laying their eggs on your crops, these eggs of course turn into caterpillars and will decimate cabbage plants.
Cabbage root fly
Cabbage root fly is a small grey fly a bit like a small house fly. It lays it's eggs at the base of cabbage seedlings, the eggs hatch into maggots and then burrow down to feast on the new roots of your plants.
Symptoms: Young plants will begin to wilt and eventually stop growing. The leaves will start to take on a bluegreen colour. If you bite the bullrt and pull up the plant you will see white maggots tucking into the roots.
Control: The best organic method of control is to cover your calabrese with bionet (micromesh) to stop the fly laying it's eggs. Make sure the net is sealed all the way round to prevent access by the fly.
Cabbage collars. You can either buy or make these yourself from roofing felt or carpet underlay. The collars are a circle of material covering the soil around the base of the plant which helps prevent the root fly laying its eggs around the stem and stops the maggots burrowing down to the roots.
Nematodes. These are naturally occuring microscopic worm which attacks the larvae of the cabbage root fly. The nematodes are in your garden soil anyway you're just increasing the numbers. It is a non chemical product so is safe for use around pets and children. You will need to do a couple of applications but in my opinion it's well worth it as you'll also protect a whole host of other crops.
Cabbage White Caterpillars
The caterpillars of the cabbage white butterfly will reduce your plants to a skeleton within a couple of days so clearly it's best to keep on top of them. Look out for the yellow eggs of the butterfly under the leaves and brush them off. It's much easier to remove the eggs than the caterpillars so this is well worth doing. The caterpillars in the photo are babies, they'll get a lot bigger and do a lot more damage if you let them! The best and easiest method however is to cover your crop with bionet as with root fly.
The Cabbage whitefly is an aphid (Like a greenfly, except white), it is less troublesome than other cabbage pests but worth keeping an eye on. The adults are tiny white insects which you'll find on the underside of the leaves. They produce a sticky substance called 'honeydew' which will probably cause a grey mould later. Remove any yellowing leaves at the base of the plant as they may be harbouring aphid eggs. You can wash off whitefly, honeydew and grey mould with a strong jet of water.
Clubroot is one of the most tricky diseases you'll encounter in the garden but with proper precautions it can be successfully controlled. If you start a new vegetable garden the chances of having clubroot are pretty slim and you can prevent it entering quite easily. If you do get clubroot the cysts survive for up to 9 years in the soil. You won't be able to grow any of the cabbage family (Brassicas) until it's gone so you've been warned! The disease usually arrives in your garden through infected transplants or by walking from infected soil into a virgin patch. If you have an isolated garden you are unlikely to get it whereas you need to be more careful in established allotments.
Symptoms: Poor growth with wilting leaves of a reddish-purple colour. If you pull up the roots you'll see swollen, knobbly deformed growth with a pungent foul odour. In more advanced cases the roots will have dissolved into a slimy pulp.
Prevention: If you have clubroot already seek out varieties with resistance to the disease, this will be clearly marked as an advantage on the pack. Otherwise you'll just have to live with it, you can minimise it's effects by doing the following:
- Not composting your brassica roots, burn them.
- Don't sow brassica famiy green manure. (Mustard, Rape)
- Start your plants in modules. (I'd recommend that anyway).
- Lime the soil the previous Autumn to make it more alkaline (Clubroot likes acid conditions).
- Grow in raised beds as clubroot likes wet conditions.
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