Effects of mixed cropping of herbs on the population and parasitism of cabbage pests

Population dynamics of cabbage pests including the cabbage aphid (CA), Brevicoryne brassicae, the diamond back moth (DBM), Plutella xylostella and the cabbage white butterfiy (CWB), Pieris rapae crucivora and their natural enemies were compared in the plots of monocropped cabbage without insecticide application, cabbage mix-cropped with nastatium, Tropaeolum majus, cabbage mixcropped with German chamomile, Matricaria recutita and monocropped cabbage with insecticide application. Significant difference in the population of each pest was observed at its peak. The average number of CA on the cabbage with German chamomile was larger than that on other treatments at 17 days after planting (DAP). On the other hand, the levels of larval population of DBM in the plots of monocropped cabbage with insecticide application and mix-cropped chamomile were relatively high at 45 DAP. Meanwhile the larval population of CWB was different at 31 DAP between four treatments, namely monocropped cabbage without spraycabbage mix-cropped with nastatiumcabbage mixcropped with German chamomilecabbage with insecticide spray. The average numbers of CWB eggs laid in the two mix-cropped plots were less than those in the plots of monocropped cabbage with and without insecticide application. The parasitism rate in CWB by Apanteles glomeratus in the nastatium-mix-cropped plots was significantly high at 52 DAP. The parasitism rates in DBM by Cotesia plutellae were not significantly different between the treatments throughout the experiment.