A Phenology Model for Asian Gypsy Moth Egg Hatch.

Phenology models are useful tools in pest management interventions, biosecurity operations targeting alien invaders, and answering questions regarding the potential for range expansion/shift. The Gypsy Moth Life Stage model (GLS) has been used to predict the invasive range of the North American gypsy moth (Lymantria dispar dispar Linnaeus [Lepidoptera: Erebidae]) in North America and New Zealand. It has been used to examine the role of supra-optimal temperatures in range expansion/stasis/retraction. However, GLS has also been used where the target organism is the Asian subspecies L. d. asiatica Vnukovskij, despite observed differences between the predominant phenotypes of the two subspecies in the temperature requirements for egg hatch and the absence of egg phenology model parameters specific to the Asian phenotype. Here we describe the results of temperature and exposure duration on the timing of Asian gypsy moth egg hatch, and we present phenology model parameters for the Asian phenotype. Sum of squared differences (observed minus predicted day of median egg hatch) was reduced from 7,818 d2 (North American parameters) to 178 d2. Days of simulated median egg hatch differed from the observed days by 0-7 d (x¯=0.2; SD=3.1). The pattern of simulated egg hatch closely mimicked the irregular pattern of observed egg hatch from the temperature regimes of our experiment. Egg hatch is arguably the most important life cycle event in gypsy moth population suppression/eradication interventions and in estimating their potential invasive range. The model parameters described here produce accurate predictions of Asian gypsy moth egg hatch.