Physical and chemical defences of pods and seeds of white mustard (Sinapis alba L) against tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae)

Adult tarnished plant bugs (Lygus lineolaris) fed 5-10 times less frequently on seeds within pods of white mustard (Sinapis alba L.) than on seeds within pods of canola (Barssica napus L.) in no-choice feeding tests in the laboratory. The presence of long, sharp spines (trichomes) on pods of 3. alba did not account for all of the difference in feeding on this mustard and on the smooth pods of canola because the feeding rate on shaved pods of S. alba was only twofold higher than on unshaved controls. Lygus lineolaris fed four times less frequently on seeds within pods of a commercial cultivar than on seeds of a near-isogenic low-glucosinolate line of S. alba, suggesting that it is the high concentration of the glucosinolate ''sinalbin'' in seeds that largely determines the low rate of feeding of L. lineolaris on this species. Plant breeders are currently developing low-glucosinolate lines of mustards such as S. alba for the oilseed market. Seed damage by L. lineolaris in an oilseed S. alba likely will be considerably higher than currently occurs in the mustard S. alba.