Introduction

Techniques of crop husbandry, including alterations in cropping systems and manipulation of cultivation practices, may provide control of weeds and pests, as well as diseases. Reducing the survival and spread of soil-borne diseases has been a particular objective of such cultural practices. Manipulation of microclimate in crops under glass can help to reduce levels of disease, and especially of pathogens favoured by high humidity.

Cropping systems

One of the advantages of crop rotation is that pathogens specific to a particular crop may be starved out in the absence of their hosts. Inoculum of pathogens surviving on crop residues can be reduced by incorporation of these residues into the soil (Section 4.2). Degradation of residues by saprophytic microorganisms in the soil will deprive the pathogen of a food source. Unless the pathogen has a resistant spore or sclerotial stage, it may perish. Rotational systems of growing have, however, declined considerably in the UK over the past 30 years. Many growers of protected crops tend to specialise, growing one or two vegetable or soft fruit crops such as tomatoes, cucumber, lettuce or strawberry. Planting of consecutive cereal crops is now common practice in some parts of the UK, and some farmers have raised cereals on the same land for 10 years or more.