AbstractThe antibiosis of crucifers to flea beetles, Phyllotreta cruciferae (Goeze), was compared for Brassica juncea L., B. napus L., and B. rapa L. with low antixenosis, B. carinata L. and Sinapis alba L. with moderate antixenosis, and Thlaspi arvense L. with high antixenosis. Adult flea beetles collected from the field in early spring fed actively on intact or excised leaves of all plants except T. arvense. The beetles survived, and gained weight and fat on the Brassica species and S. alba, but not on intact foliage of T. arvense. No antibiosis was detected in any of the Brassica species or in S. alba. Intact foliage of T. arvense was so antixenotic that beetles probably starved rather than suffered from antibiosis. A low level of antibiosis was detected in excised foliage of T. arvense where the antixenosis was lost. These experiments show that estimates of beetle survival, dry weight, and fat content can be used in the laboratory to test small numbers of candidate plants for antibiosis. However, the level of antibiosis appears to vary less among Brassica species and related plants than does the level of antixenosis, and so the latter is a more promising type of resistance for use against flea beetles in canola.