EFFECTS OF STRIP CROPPING ON GROUND DWELLING INSECT ABUNDANCE AND DIVERSITY

Summary

Beneficial ecosystem services of strip-cropped systems, such as reduced pest pressure, increased nutrient uptake and higher crop yields with less agrochemicals are widely reported, but studies on the effects of strip-cropping on ground dwelling insects, and the Carabids especially, are lacking. Natural enemies, such as Carabids, have the potential to provide sustainable and ecofriendly pest insect control. In this study, we conducted experiments on the effects of strip-cropping cabbage, Brassica oleracea var. capitata (cultivar Castello), and faba bean, Vicia faba (cultivar Sampo), on ground dwelling insects, and compared the results to monoculture crops. Sampling was done by pitfall trapping the insects and identifying them. Trapping was done in 4 periods, each lasting 7 days, followed by 14 days of letting the insect assemblages recover for the next week’s trapping. The whole trapping period lasted from 12.6. to 21.08.2018, a total of 10 weeks. Insects were identified to taxonomic ranks varying from genus to subclass. Carabid beetles were of special interest and were all identified to genus. In total there were 21 genera of Carabids, and this group was of keen interest due to it being comprised mostly of predatory insects and thus capable of biological pest insect control. Strip-cropping is hypothesized to increase abundance of predatory insects, which makes abundance of Carabids a useful indicator for assessing the effect. Faba bean on its own was observed to attract the most insects. The positive effect of faba bean on insect abundance appeared also to have been carried over to the strip-cropped system. This suggests that with the cabbage and faba bean crop combination, insect abundance and diversity could be manipulated. The strip-cropped system had the highest insect diversity, giving further proof for beneficial effects of strip-cropping via increase in diversity.