Comparing simple versus diverse trap crops for control of the crucifer flea beetle (Phyllotreta cruciferae)

The crucifer flea beetle, Phyllotreta cruciferae Goeze (Coleoptera: Chrysomelidae: Alticinae) is an oligophagous pest of Brassica crops. In the Pacific Northwest, many growers rely on Brassica crops as a major component of mixed-vegetable production, and flea beetle damage lowers marketable yields of these crops. In plots both west (Mt. Vernon, WA) and east (Moscow, ID) of the Cascade Mountains, we have been evaluating different species species-compositions of trap crop plantings to draw flea beetles out of broccoli (B. oleracae L. var. italica ). We compared single- and mixed-species plantings of the three most attractive trap-crop species identified in a previous field trial ( Brassica napus, Brassica juncea, and Brassica campestris L. var. chinensis) for their abilities to attract flea beetles and protect adjacent broccoli. Flea beetle (P. cruciferae) populations in trap crops were tracked using D-vac suction, while visual observations were used to monitor flea beetle populations and damage in broccoli. We found that the broccoli adjacent to diverse polycultures of all three trap-crop species attained the greatest dry weight. Our results thus far suggest that multi-species trap crops are a particularly effective way to protect broccoli from flea beetle damage.