Cabbage maggot, Delia radicum (L.) (Diptera: Anthomyiidae) is a serious pest of Brassica such as broccoli (Brassica oleracea var. italica Plenck) and cauliflower (B. oleracea L. var. botrytis) in California's Central Coast. Since there are limited non-chemical options available for growers to manage D. radicum, there is an urgent need to develop alternative tactics. The objective of this study was to determine the effects of side-by-side plantings of turnip (Brassica rapa var. rapa L.), lettuce (Lactuca sativa L.), cauliflower, and cabbage (B. oleracea L. var. capitata) with broccoli on D. radicum infestation. In 2013 and 2014, the experiments were conducted in Salinas, California. Significantly greater numbers of eggs and larval feeding damage were found on turnip compared with broccoli. Lettuce (Asteraceae), a non-Brassica crop, was compared with broccoli; however, lettuce did not reduce oviposition or larval feeding damage on broccoli. The larval feeding damage on cauliflower was significantly lower than on broccoli when planted side-by-side. The effects on cabbage were not significantly different from broccoli in terms of oviposition and larval feeding damage. This new information generated from the Central Coast of California will be further utilized to develop a trap crop to effectively tackle the D. radicum problem in Brassica fields.
Keywords: Central Coast of California; Delia radicum; Salinas Valley; broccoli; cauliflower.