An egg-hatch model for codling moth, Cydia pomonella (L.) for Pennsylvania apple orchards

Codling moth (CM), Cydia pomonella (L.) (Lepidoptera: Tortricidae), is currently the most important internal fruit-feeding pest of apples in Pennsylvania. Accurately predicting the timing of egg-hatch events for this pest will allow growers to more effectively time insecticide applications. The initial PETE (prediction extension timing estimator) model is currently used to predict life cycle events for many fruit pests including CM. The PETE model for CM egg-hatch prediction (PETE-CM) has never been validated in apple orchards of Pennsylvania. Therefore, a series of field and laboratory observations were conducted in 2007 and 2008 on oviposition and daily egg-hatch of CM in apple orchards of Pennsylvania. The observed percent cumulative egg-hatch was used to develop two PA logistic constrained and unconstrained models. The egg-hatch predictions by these PA models were compared with the egg-hatch prediction generated by the PETE-CM logistic model to either validate this model or to develop a new egg-hatch model (PACM-EH model) for this apple growing region. Our findings showed that during the first generation, the PACM-EH model predicted a delay in the cumulative percent egg-hatch by ~60 degree days (DD) at 10 percent egg-hatch when compared to the PETE-CM model. The PACM-EH model also showed a delayed percent cumulative egg-hatch of ~85 DD and ~75 DD at the 50 and 90 percent cumulative egg-hatch intervals, respectively. During the second generation of CM, the model showed a delayed percent cumulative egg-hatch of ~67 DD and ~62 DD at 50 and 90 percent cumulative egg-hatch periods, respectively.