Modeling the Phenology of Asian Citrus Psyllid (Hemiptera: Liviidae) in Urban Southern California: Effects of Environment, Habitat, and Natural Enemies.

Modeling can be used to characterize the effects of environmental drivers and biotic factors on the phenology of arthropod pests. From a biological control perspective, population dynamics models may provide insights as to when the most vulnerable pest life stages are available for natural enemies to attack. Analyses presented here used temperature and habitat dependent, instar-specific, discrete models to investigate the population dynamics of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). This pest is the target of a classical biological control program with the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae). The population trends of D. citri eggs, nymphs, and adults, citrus flush growth patterns, and T. radiata activity were monitored monthly on orange and lemon trees at 10 urban sites in southern California for a 2-yr period. Cumulative D. citri egg, nymph, and adult days recorded at each site, were regressed against accumulated degree-days (DDs) to model the population dynamics of each development stage in relation to temperature. Using a biofix point of 1 January, the model predicted that 10% and 90% of eggs were laid by 198 and 2,255 DD, respectively. Populations of small and large D. citri nymphs increased slowly with 90% of the population recorded by 2,389 and 2,436 DD, respectively. D. citri adults were present year round with 10 and 90% of the population recorded by 95 and 2,687 DD, respectively. The potential implications of using DD models for optimizing inoculative releases of natural enemies, such as T. radiata into citrus habitat infested with D. citri, are discussed.