Use of the Pherocon AM Trap as a Scouting Tool for Predicting Damage by Corn Rootworm (Coleoptera: Chrysomelidae) Larvae

Damage by northern and western corn rootworm, Diabrotica barberi Smith and Lawrence and Diabrotica virgifera virgifera LeConte, respectively, larvae was assessed in 34 cornfields in 1980 and 1981 where adult populations had been monitored the previous August and early September by using unbaited Pherocon AM traps and insect counts taken on entire corn plants. Correlations between population estimates and subsequent damage ratings in 1980 were significant, averaging 0.72 for both sampling methods. The following year, correlations were not as high, averaging 0.32 for the plant count and 0.39 for the Pherocon AM trap, and significant correlations with damage for both methods were obtained for only a single sampling period in mid-August. Regression equations describing the relationship between these adult population estimates and subsequent larval damage are given. These equations result in significant R2 values of 0.26 for the Pherocon AM trap and 0.27 for the plant count. Because the Pherocon AM sampling technique predicts larval damage as well as the currently standard plant-count method and may have advantages over it, a sampling plan is proposed for the use of the Pherocon AM trap as a tool for scouting corn rootworms.