Phenology of Asian Citrus Psyllid (Hemiptera: Liviidae), With Special Reference to Biological Control by Tamarixia radiata, in the Residential Landscape of Southern California

Since its discovery in 2008, the pestiferous Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), has become widely established in residential citrus trees throughout southern California. In 2011, Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), a host-specific parasitoid of D. citri, sourced from Punjab Pakistan, was introduced into California as part of a classical biological program aimed at suppressing D. citri populations in urban areas. Despite these release efforts, little is known about the population dynamics of D. citri in urban citrus or the efficacy of T. radiata in controlling psyllid populations in urban-grown citrus. To address this shortcoming, the population phenology of D. citri was monitored biweekly for 2-3 yr on five different host plants (Rutaceae) at 11 residential sites across Riverside and Los Angeles Counties in southern California. Citrus flush growth patterns and parasitoid activity levels were also assessed. Urban D. citri populations were present year round at each site, with highest densities occurring over July through November. Temperature was an important indicator of overall D. citri densities with positive correlations across all life stages. Regularly flushing lime trees consistently supported the highest densities of psyllid eggs and nymphs, while equally vigorous flushing curry leaf plants supported the highest adult densities. While T. radiata activity was detected at all sites, average year-round percent parasitism was low throughout the study, averaging < 5% in 2012, 2013, and 2014.