Feeding deterrency of flavonoids and related phenolics towards Schizaphis graminum and Myzus persicae: Aphid feeding deterrents in wheat

A number of naturally occurring flavonoids have been tested for their feeding deterrent activity against two aphid species, Schizaphis graminum and Myzus persicae. Most flavonoids, including a number of dihydrochalcones related to phloretin, showed strong deterrency at concentrations well within the range often found in plants. Flavanone and flavone glycosides showed weak feeding deterrency relative to their corresponding aglycones. S. graminum and M. persicae responded similarly towards the compounds tested. The feeding deterrency of wheat extracts towards S. graminum was confined to the phenolic fraction, which included the flavone tricin. The more polar phenolic fraction showed the strongest feeding deterrency towards S. graminum.