Abstract/Summary

Soil borne pathogens are especially difficult targets for control by environmentally sustainable methods. The reasons for this include; wide host range providing substantial numbers of alternative hosts including weed species; inoculum distribution varies in depth and intensity across fields and down the soil profile; soil water movement provides means for the redistribution of sexual and asexual propagules; genetic resistance in host species may be limited and variable in effect and the intensity of cropping limits the opportunities for rotational growing. Manipulation of crop husbandry is steadily re-emerging as a key ingredient in disease control strategies. This requires careful strategic planning of crop cycles and the use of resources. Implementing these plans demands continuous monitoring and the introduction of further elements of control in order to maintain crop health. The successful use of husbandry control is critically reviewed with particular reference to Clubroot Disease of Brassica crops (caused Plasmodiophora brassicae Wor.). Understanding the impact of nutrient ions and pH on the germination, movement and host colonisation by primary zoospores related to the presence of benign microbes in the soil allows the formulation of coherent husbandry control. Boron, calcium and nitrate salts of nitrogen diminish the germination capacity of resting spores, motility of primary zoospores and their fitness for colonisation. Calcium encourages the expansion of populations of benign microbes. Hence crop fertiliser strategy, soil management and drainage policy can be combined into a sustainable control system for a previously intractable pathogen of horticultural crops.