Seed treatments using the fungicide benomyl at 1.1 and 2.2 per cent w/w protected seedling rape from infection by Leptosphaeria maculans under glasshouse conditions but in field experiments with natural infection no worthwhile control of the disease was obtained. Benomyl applied as a spray to rape seedlings in field experiments gave variable but mainly poor control At the maximum rate tried it increased yields at only three out of eight experiment sites.