Plant Doctor Archive

Club root in brassicas

I HAVE club root in my vegetable garden. I applied lots of lime and the pH is around 6.8-7.0. Do you know how I can get rid of it, preferably organically?

ONCE club root gets into the soil it becomes almost impossible to grow brassicas, like cabbage, broccoli and cauliflower. It causes the roots to become stunted so the top growth doesn't develop properly. The worst thing about it is the disease can remain in the soil for up to 10 years, and that's only if there are no brassicas grown in it over that time - including weeds belonging to the crucifer family, such as wild turnip, wild radish and mustard, and related ornamentals.

You could try improving drainage as much as possible as the disease symptoms are worse in wet soil, and adding more lime to raise the pH to above 7.2. But the best answer would be to find another spot in your garden in which to grow your brassicas. There are fungicides, such as Greenguard, which some gardeners dip their brassica plants in before planting, which give some measure of control.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.