Going too far? Trap crop distance and flea beetle control

The crucifer flea beetle, Phyllotreta cruciferae Goeze (Coleoptera: Chrysomelidae: Alticinae), is an oligophagous pest of Brassica crops. In the Pacific Northwest, broccoli and its relatives are major components of mixed-vegetable production, and flea beetle damage lowers marketable yields of these crops. In previous work we found that a diverse trap crop consisting of several Brassica species (Brassica napus, Brassica juncea, and Brassica campestris L. chinensis) was a particularly effective way to protect broccoli (Brassica oleracea L. var. italica) from flea beetle damage. In plots both west (Mt. Vernon, WA) and east (Moscow, ID) of the Cascade Mountains, we have been evaluating optimal trap crop distances that will effectively draw flea beetles out of broccoli, while preventing over-spilling into the protection target. Flea beetles (P. cruciferae) populations in trap-crop species were tracked using D-vac suction, while visual observations were used to monitor flea beetle populations and damage in broccoli.