Seasonal Abundance and Degree-day Prediction of Sod Webworm (Lepidoptera: Pyralidae) Adult Emergence in Virginia

Abstract

Sod webworm larvae are pests of commercial and ornamental turfgrasses. Sixteen sod webworm species occurred from May to October in Virginia; some were multivoltine and others were univoltine. Number of generations and flight peaks differed among species. Calendar date was a better flight peak predictor than degree-days (DD) for most species. However, DD models generated from pooled data were the best flight peak predictors for three species. Pediasia trisecta (Walker) adults first appeared at 271 ± 25.5 DD (C) (488 ± 45.5 DD [F)) and 211 ±23.0 DD (C) (380 ± 42.5 DD [F)) in 1981 and 1982, respectively (10°C base temperature). P. trisecta took 541 DD (C) (975 DD [F)) and 610 DD (C) (1,906 DD [F)) from the beginning of the first generation to the second and 746 DD (C) (1,343 DD [F)) and 730 DD (C) (1,315 DD [F)) from the second to the third generation during 1981 and 1982, respectively. Pooled models were more reliable for predicting adult flight peaks to identify optimal times to apply insecticidal sprays for some species, while calendar dates were best for others.