Scientific Note Evaluation of a commercially available ELISA kit for quantifying imidacloprid residues in Erythrina sandwicensis leaves for management of the Erythrina gall wasp, Quadrastichus

The erythrina gall wasp (EGW) , Quadrastichus erythrinae Kim 2004, was first detected in Hawaii in 2005 and has been infesting-ana killing Erythrina trees throughout the island chain since. It is believed EGW originated from Africa (Messing et al. 2009). Its host range appears to be limited to Erythrina; its geographic range already includes much of Asia and the Pacific. In North America, EGW has recently become established in south Florida and it is expected that introductions will occur to southern California (Smith et al. 2007). Observations indicate that a highly favored host is E. variegata L., but numerous species, including the Hawaiian endemic, E. sandwicensis O. Deg are severely injured and killed. Erythrina are warm-loving plants with about 115 species in the genus. It is expected that EGW will expand its geographic range to meet that of its host Erythrina with some restrictions due to climate (Li et al. 2006). Successful management of newly introduced pests is most probably achieved when multiple approaches are considered (e.g., Hain 2006). Hawaii has a major effort underway in classical biological control and it is hoped that introduced natural enemies will provide a long-term management solution for EGW populations (Hawaii Department of Agriculture 2008). The vagaries of prescribed introductions, along with environmental heterogeneity, differing resource values, cultural and social impacts, and potential effects on nontarget organisms (including humans), all suggest there is a need for the development of multiple tools for management. Indeed, insecticides will continue to play an important role against newly introduced alien species and for protecting particularly valuable resources. For EGW, the active ingredient imidacloprid has been demonstrated to have good activity. Systemic applications of imidacloprid have been effective in killing EGW larvae, and imidacloprid residues in host leaves have been correlated with EGW mortality (Xu et al. 2006, 2008). Applications by stem-injection or soil drench are seen as being valuable for protecting or perhaps rehabilitating high-value Erythrina trees, especially ornamentals. In addition, strategic applications of systemics could help reduce new establishments, for example, by treating trees near ports considered likely for introductions. The ability to simply and reliably determine residual concentrations of imidacloprid in Erythrina tissues is important for efficient insecticide use, development of effective management plans, and regulatory oversight. Residual concentrations of imidacloprid in plant tissues are typically determined by high performance liquid chromatography (HPLC). This technique is limited by incomplete resolution of metabolites and relatively high detection …