Soil persistence and distribution of ethofumesate applied to autumn‐sown perennial ryegrass for Poa annua control

Summary: A bioassay technique based on Poa annua growth showed that ethofumesate applied at 2.0 kg/ha in October to a newly‐sown ryegrass (Lolium perenne) sward had a half‐life of just over 8 weeks. After 7 months there was still sufficient herbicide present to cause about a 50% reduction in P. annua growth. The movement of ethofumesate, as measured in soil cores taken 15 months after spraying, was confined mainly to the upper 2 cm of the soil profile. Seeds on the soil surface at spraying were very sensitive to ethofumesate. The implications of the findings for weed control in newly‐sown grass leys are discussed.