An Evaluation of Insect Resistance in Broccoli, Brussels Sprouts, Cabbage, Collards, and Kale

Resistance to Pieris rapae (L.), Brevicoryne brassicae (L.), Myzus persicae (Sulz.), Phyllotreta vittata (Fab.), and Lygus spp. was recorded in the plant (Brassica oleracea L.) varieties of broccoli, Brussels sprouts, cabbage, collards, and kale. In these varieties no resistance was found to Phyllotreta cruciferae Goeze and Psylliodes punetulata Melsh. nor to Trichoplusia ni (Hbn.) and Plutella maculipennis (Curt.) which existed at low densities. No one plant variety was most or least resistant to all the insect species; each plant variety had its own pattern of resistance. Resistance of collards and kale to P. rapae resulted principally from increased exposure of larvae of P. rapae on the open leaves to the parasites, Phryxe vulgaris (Fall.) and Apanteles glomeratus (L.). Plant resistance was based on both intrinsic (physiological) and extrinsic (ecological) factors, and the interaction of both.