Some effects of weed control on the numbers of the small cabbage white (Pieris rapae) on brussels sprouts.
Abstract
The results of experiments conducted during 1968 showed that the presence of weed within the crop provides a suitable habitat for some of the ground-living arthropods which are important predators of P. rapae. Harpalus rufipes was particularly dependent on ground-cover. The higher number of predators on the weedy plots significantly reduced survival of P. rapae as compared to that on hoed plots. Although fewer eggs were laid by P. rapae on those plots with many flowering weeds the difference was not significant to the 5% level. Pest numbers were low but any advantageous effects of weed were outweighed by the harmful effects of competition between the weed and the crop. Yields were highest on the plots which were kept free from weeds. F.s.- M.Y.