Hydroprene Prolongs Developmental Time and Increases Mortality of Indianmeal Moth (Lepidoptera: Pyralidae) Eggs

Eggs of the Indianmeal moth, Plodia interpunctella (Hübner), were exposed to the labeled rate of hydroprene (1.9 × 10−3 mg [AI]/cm2) sprayed on concreted petri dishes. These eggs were exposed for 1, 3, 6, 12, and 18 h and until hatching (continuous exposure) at temperatures of 16, 20, 24, 28, and 32°C and 57% RH until the emergence of first instars. The developmental time and egg mortality were significantly influenced by temperature and exposure periods. At 16°C, hydroprene did not cause differences in developmental time when eggs were exposed for different periods. At temperatures >16°C, both exposure period and temperature influenced developmental time. The maximum developmental time (15.0 ± 0.2 d) occurred at 16°C, and the minimum developmental time (3.2 ± 0.3 d) occurred at 32°C. Mortality increased when eggs were exposed to hydroprene for longer periods at all of the five tested temperatures. The greatest mortality (81.6 ± 2.1%) occurred when eggs were continuously exposed on treated surfaces at 32°C. We used developmental time instead of rate (1/developmental time) to fit simple linear or polynomial regression models to the development data. Appropriate models for developmental time and mortality were chosen based upon lack-of-fit tests. The regression models can be used in predictive simulation models for the population dynamics of Indianmeal moth to aid in optimizing use of hydroprene for insect management.