Population Studies of Stem Eelworm (Ditylenchus dipsaci) in Microplots, Field Plots and Fields in the North of England under Different Crop Rotations

Abstract

SUMMARYObservations of soil populations of Ditylenchus dipsad (Kühn) Filipjev were made in the north, of England from 1963 to 1969. Samples were taken in spring and autumn or winter from the same 14 commercial fields where oat cultivars susceptible to D. dipsad had been damaged previously by this pest, from field plots under different rotations and different weed control programmes. and from microplots under different crop rotations.In fields and field plots growing cereals, populations generally increased during summer and decreased during winter. Large increases occurred, when oats were grown. With swedes, potatoes and ley, slight reductions occurred daring summer and larger reductions during winter. Seven of the 14 sites contained populations below detectable levels after 2–8 years without an oat crop; in the remainder, detectable numbers were still present 1–7 years after an oat crop. Field plots receiving no herbicide maintained larger soil populations of D. dipsaci. Approximately 40–60 per cent of oat plants were damaged in crops grown after one or two years’ barley and about 20 per cent after three years’ barley whether or not herbicides had been applied.In microplots kept weed free, three years of barley, grass, or barley/ grass rotation, three or four years’ fallow or three or four years’ weeds reduced soil levels of D. dipsaci by 99–100 per cent. After all these rotations one oat crop increased the soil population to detectable levels and a second oat crop showed symptoms of damage.