Effects of fungicides and insecticides on mildew, viruses and root yield of swedes

Fungicides, applied to control powdery mildew (Erysiphe cruciferarum Opiz ex L. Junell) on swedes (Brassica napus L. var. napobrassica Peterm), increased root yield by up to 66, 57 and 45 per cent in 1974, 1975 and 1976 respectively. In 1975, early‐sown swedes yielded more than late‐sown swedes when sprayed to control mildew. Untreated swedes gave similar yields whether sown early or late. Early sowing also increased the incidence of virus diseases. Insecticide sprays decreased aphid numbers but had little effect on virus incidence; they significantly increased root yield when tested in 1975 but not in 1976.