Seasonal Damage by Greenbugs (Homoptera: Aphididae) to a Resistant and a Susceptible Variety of Wheat1

Abstract

A 2-year field study was conducted in Oklahoma to evaluate damage by biotype C greenbugs ( Schizaphis graminum [Rondani]) to a susceptible (S), ‘TAM W-101,’ and a resistant (R), ‘TAM W-101/Amigo,’ hard red winter wheat. Fall and spring infestations were compared by measuring yield components and visible damage. Significant differences were found between the R and S lines in number of fertile tillers, grain yields, number of seeds per plant, and damage ratings. These differences occurred in one fall season and both spring seasons. The data showed that fall damage for both R and S was generally more severe than spring damage. Plants damaged in the fall appeared to recover, but ultimately exhibited a marked decrease in grain yield at spring harvest. Fall economic thresholds were less than 10 greenbugs per plant, while spring economic thresholds were less than 20 greenbugs per plant for the S variety.