Presence dynamics in selected winter oilseedrape pests during the spring period in different cropping systems

Apart from the main issues related to weeds, a key factor with respect to the organic growing of winter oil seed rape is the presence of pests. The number of winter oil seed rape pests has rapidly increased in the course of the past twenty years due to the expansion of cultivated land coupled with the prevailing use of conventional technology. We have monitored the presence of selected groups of winter oilseed rape pests in organic and conventional farming, in particular, the presence of stem weevils (Ceutorhynchus napi Gyll., Ceutorhynchus pallidactylus Mrsh.), cabbage flea beetles (Phyllotreta Stephens spp.), cabbage stem flea beetles (Psylliodes chrysocephala L.) and cabbage root flies (Delia radicum L.). With respect to stem weevils, we have monitored the presence of recently emerged larvae. We have noticed a significant differences in pest abundance between organically and conventionally grown plots. A very low level of stem weevil larval parasitisation by hymenopteran parasitoids was only recorded during one of the four monitored years (6.8% in organically and 16.7% in conventionally grown plots). A better understanding of pest peak abundance periods may contribute to the enhancement of integrated control systems