An integrated approach towards Asian citrus psyllid management: Ant baiting and biological control

Over the next five years, chemical and cultural control of the Asian citrus psyllid (ACP) could cost California’s citrus industry $1.1 billion, though establishment of ACP-vectored huanglongbing could cause its collapse entirely. As part of a comprehensive approach aimed at long-term management of ACP in California, I am investigating strategies to improve biological control utilizing its parasitoid, Tamarixia radiata. A major impediment to this strategy is the Argentine ant, Linepithema humile, which tends ACP for honeydew, providing protection from natural enemies in the process. I conducted experiments to examine the efficacy of a long-term, low-toxicity ant baiting strategy and quantify the impact of ant control on ACP parasitism. In a two-year replicated field study, nearly a thousand flush samples were examined from a total of 98 trees in 5 urban and research citrus groves across southern California. On half of all experimental trees, L. humile activity was either prevented using a sticky barrier or suppressed using dilute poison baits. When L. humile activity was reduced utilizing either strategy, ACP parasitism by T. radiata increased by 65-100% and generalist predator abundance tripled. Using this low-toxicity baiting protocol, L. humile activity declined by 75-90% within 3 days of treatment and near-complete suppression of activity was achieved over a 3-month baited period. Three months after baiting cessation, Argentine ant activity remained significantly below pre-baited levels. We conclude that this low-toxicity baiting protocol is an effective long-term management option for L. humile in citrus which results in critical increases in ACP parasitism and predation.