Disease control by plant sanitation

Abstract

This is the simplest and no doubt one of the earliest of disease control measures to be used. Destruction of diseased plant material, whether in the form of plants in the fields or crop residues after harvest, is an obvious way of reducing inoculum. Sources of seasonal carry-over are considered elsewhere (p. 329) but briefly they comprise infected plant material remaining in the fields after harvest, infected plants which survive the intercrop period, infected self-sown seedlings, infected weeds or cultivated plants in gardens, infected plant products of commerce, soil borne infection, seed borne infection, diseased plant material brought in from other areas, and air borne inoculum from distant areas where diseased crops are growing. All these sources of inoculum may have to be destroyed or avoided but the first step is to find out which are involved, and to concentrate on these. Hence sanitation is selective: the presence of inoculum does not in itself prove that it plays a major part in carry-over of the pathogen although it is wise to assume that it does so unless demonstrated to the contrary. Not all infected weeds are necessarily able to pass on their pathogens to cultivated crop plants. Different physiological races are sometimes involved and this can only be determined by cross-inoculation experiments and sometimes from observations on the distribution of the disease in the field.