| The western cabbage flea beetle, Phyllotreta pusilla Horn (Chrysomelidae: Coleoptera), is often the most important insect pest of brassica crops in the Rocky Mountain region. In this study, alternative management tactics such as cultural, mechanical, and chemical controls were investigated. In these studies action thresholds were also developed.; Chinese cabbage, the cabbage cultivars 'Golden Acre' and 'Copenhagen Market' and the broccoli cultivar 'Green Goliath', were significantly most preferred. Cauliflower, Brussels sprouts, collard, kale and the cabbage cultivars 'Red Acre', 'Earliana' and 'Salad Delight' and broccoli cultivars 'Love Me Tender Hybrid' and 'Premium Crop' were significantly least preferred by flea beetles. A 40-cm in-row spacing plant density resulted in a significant decrease in flea beetle numbers in given area, but an increase in numbers infesting individual plants within that area. Flea beetle density was highest in plots with no radishes interplanted between broccoli plants. The colors Saturn green, Saturn yellow and white were significantly the most attractive to flea beetles compared to the transparent control. Allyl isothiocyanate baited traps were significantly attractive to western cabbage flea beetle adults. Traps baited with canola oil were significantly less attractive compared to allyl isothiocyanate. Increase in allyl isothiocyanate concentration up to 2% significantly increased the attractiveness of the traps. Thiodan (endosulfan) and Asana (esfenvalerate) were significantly the most effective insecticides. Margosan-O, SunSpray, Azatin, and diatomaceous earth were significantly the most effective tested repellents. Head diameter was significantly larger in plots maintained at 0-beetles per plant threshold compared to head diameter from plots maintained at 10-beetles per plant threshold and the control. Yield obtained from plots maintained at 0, 2 and 5-beetles per plant thresholds in 1997 and 0-beetles per plant threshold in 1998 was significantly higher compared to the 10-beetles per plant threshold and the control. Greatest head size reduction and yield loss occurred at the 10-beetles per plant threshold. The five flea beetles per plant threshold appears to be an appropriate action threshold for flea beetle control on seedling brassica crops. |
