Evaluation of Gallery Injection for Management of Invasive Shothole Borers ( Euwallacea spp.) Associated with Fusarium Dieback in High-Value Trees

Invasive shothole borers ( Euwallacea spp.)(ISHB) and their associated fungal pathogens cause substantial damage to urban and riparian trees, creating a need for diverse management approaches to accommodate different infestation scenarios. Gallery injection, a technique in which small volumes of pesticide are delivered directly into active beetle galleries, has not previously been evaluated for ISHB and may provide a localized treatment option that limits pesticide applications to infested portions of the host. The objective of this study was to evaluate gallery injection as a management approach for ISHB, compare the efficacy of different active ingredients delivered using this method, and quantify the volume of solution that could be delivered into active galleries under field conditions. Field trials were conducted on Platanus spp. in Southern California. Active galleries were verified prior to treatment, and beetle activity was assessed following injections. Gallery injections with emamectin benzoate and imidacloprid significantly reduced gallery activity relative to untreated controls, whereas acephate provided intermediate control. Bacillus subtilis did not significantly reduce gallery activity during the study period. The volume of solution delivered into individual galleries ranged from 0.01 mL to 0.4 mL. These findings demonstrate the potential of gallery injection for suppressing ISHB activity. Although the technique is unlikely to be practical for largescale management of widespread infestations, it may provide a useful option for newly infested trees, lightly infested trees, or high-value trees where localized intervention is desirable.