Sowing mixtures of Brassica trap crops is recommended to reduce Phyllotreta beetles injury to cabbage

Abstract

We studied the extent of damage by cabbage flea beetles on four different Brassica species in a two-year field experiment (2009–2010) at two locations in Slovenia. The entire experiment was based on testing oilseed rape, white mustard and oil radish as potential trap crops to protect cabbage from cabbage flea beetles. A significant influence of the Brassica species on the feeding by the flea beetles was confirmed at both locations. The damage index on oil radish was the highest throughout most of the growth period, whereas oilseed rape and white mustard were preferred only during a certain growth period. The initial damage by the cabbage flea beetles occurred in the first half of May, whereas the greatest damage occurred at the beginning of July. The research shows that the onset of cabbage flea beetle feeding can be controlled in a medium-late cabbage cultivar using trap cropping. However, because none of the tested trap crops strongly attracted the flea beetles throughout the entire growing period of the crop, we recommend sowing mixtures of crops for cabbage production; thus, each of the three Brassica species would attract phytophagous insects during a particular part of the cabbage growing season.