How to cope with blackleg on cabbages

This fungus might be pretty rare these days, but it’s still worth knowing how to deal with it

- Bill Kerr

Blackleg (Leptosphaeria maculans) is less widespread these days on account of better sanitation in seed production.

However, you can still get the odd infected seed, and it’s worth knowing how to deal with this fungal pathogen should you find any plants infected with it.

The symptoms in the field are seen as purple lesions at the base of the stem and usually start on one side and gradually encircle the stem, after which the plant may fall over. Infected plants are easily spotted, because they start turning yellow and look unhealthy.

If you take a knife and cut diagonally down the discoloured stem, you will find black discoloration within the stem.

In the seedbed it may start on the stem, causing the plant to fall over, but it can also make circular tan patches on the leaves with black spots within, which are pycnidia. These produce asexual spores (conidia), one which infects living tissue and the other which reproduces on dead plant tissue.