Allotment plots often suffer from a variety of pests and diseases, sometimes because of poor plant husbandry by previous plot holders. These problems include onion white rot, pea & bean weevil, pea thrips, slugs, snails, wireworm, greenfly, whitefly, blackfly, mildew, caterpillars, pigeons, mice, cabbage root fly, carrot root fly, potato blackleg, potato root eelworm and Club Root. It's a wonder that we manage to produce any harvest at all!

One fungal disease that can be overcome is Brassica Club Root ( Plasmodiophora Brassica). This pest is recognised by the large swellings on the roots of the plants and can seriously affect cropping. It's particularly bad on poorly drained acid soil. A treatment in the past was Calomel, but this product has been withdrawn for health reasons plus it isn't organic.

My own plot was infected when I took it over. The swellings were so large that they broke through the surface and the rats came and ate them. The cure, which took several years to become fully effective, came in three parts.

Most important was the use of lime in the form of ground limestone. This was applied to the brassica section in two stages. Six ounces per square yard in January and another similar application in May, shortly before planting out. The reason for two applications is that the beneficial soil organisms don't like sudden changes in soil pH. This lime made the soil slightly alkaline and the fungus didn't like that. With free draining soil on the site, rain leached out the lime so that it had become slightly acid in time for the later potatoes, and potatoes do like that.

Second was the use of a strict four year crop rotation with all the brassicas being grown in the lime treated section. This rotation was chosen so that the brassicas came after the potatoes and gave the soil time to become slightly acidic for the next crop of potatoes in three years.. Also, by the time that the brassicas came round again, many of the fungal spores had died.

Finally, but not essentially, all the brassicas were raised in a general purpose compost in Rootrainers. These composts are usually free of the fungal spores and give the plants a good healthy start.

Now, club root is a thing of the past but I still follow this three pronged regime.

George Sutherland.