A survey of weeds of oilseed rape in central southern England

Abstract

SummaryWeeds in a total of 450 fields of winter oilseed rape in nine areas of central southern England were surveyed, just prior to harvest during summer 1985, to identify those that had survived herbicide treatment or had not been sprayed and, thus, were capable of re‐infestation or contamination of the harvested crop. Sixty‐two species were identified; their levels of infestation were scored and distribution within the field noted. The most frequent species was Galium aparine, which occurred in 57% of fields. Mayweeds (Tripleurospermum inodorum, Matricaria recutita and Anthemis cotula) occurred in 23% of fields and Papaver rhoeas in 21%. All other species occurred in less than 20% of fields, the most prevalent being Sonchus asper(18%). Grassweeds were relatively infrequent, reflecting the widespread use of effective graminicides; the most prevalent was Arena spp., found in 9% of fields. Although most species were distributed throughout the field, Geranium dissection (13%) and Sisymbrium officinale (7%) were virtually confined to field margins (extending 1 m into the crop) and headlands (10m into the crop), respectively. Several species exhibited a well‐defined regional distribution; Silene alba was virtually restricted to the most southern counties surveyed, whilst Papaver rhoeas and Viola arvensis were conspicuously absent from the eastern area.