Size and shape of sampling units for estimating incidence of stem canker on oil-seed rape stubble in field plots after swathing

Abstract

Further exploitation of the increasingly popular oil-seed rape crop, Brassica napus L., as a valuable break in cereal production in the U.K., is threatened by the susceptibility of the crop to a number of diseases of which the most serious is likely to be stem canker caused by Phoma lingam (Tode ex Fr. Desm.), perfect stage Leptosphaeria maculans (Desm.) Ces et de Not. (Gladders, 1977; Hewitt, 1977). This pathogen has already severely restricted the cultivation of oil-seed rape in France (Lacoste et al. 1969) and in Australia (Bokor et al. 1975; McGee & Emmett, 1977).