Temperature-Dependent Development of Immature Phyllonorycter ringoniella (Lepidoptera: Gracillariidae) and Its Stage Transition Models.

Asiatic apple leafminer, Phyllonorycter ringoniella (Matsumura), is an important insect pest of apple in Northeast Asia. Its larvae mine the leaves and are best managed by targeted sprays. Little is known about its thermal development characteristics, thus, immature P. ringoniella development was investigated under eight constant temperatures (13.3, 15.3, 20.7, 23.6, 26.1, 30.0, 32.3, and 35.0°C) in the laboratory. The total developmental period of the immature stage (egg-pupa) was inversely related to temperature and decreased from 76.4 d at 13.3°C to 25.9 d at 26.1°C. The developmental periods of eggs, larvae, and pupae ranged from 4.8 to 15.2, 15.5 to 40.3, and 5.7 to 21.6 d, respectively. Eggs, larvae, and pupae did not survive at 35.0°C. According to the ordinary linear model, the lower developmental threshold temperatures for egg, larva, pupa, and total immature stage were estimated as 6.7, 6.7, 9.6, and 7.1°C, and the thermal constants as 93.5, 286.5, 94.6, and 480.1 degree-days (DD), respectively. There were large differences among 11 nonlinear models for estimating lower and upper temperature thresholds, and small differences in estimating optimal temperature. Nonlinear temperature-dependent developmental rates were best represented by Lactin-1 model for egg and Briere-1 model for other stages. Stage transition models from eggs to adults of P. ringoniella were constructed by two-parameter Weibull function with the respective selected nonlinear developmental rate models. This study provides a fundamental understanding of thermal traits of P. ringoniella development which will be a useful tool to predict stage transition and for developing decision-based spray timings for integrated pest management.