PCR-Based Gut Content Analysis to Detect Predation of Eriococcus ironsidei (Hemiptera: Eriococcidae) by Coccinellidae Species in Macadamia Nut Orchards in Hawaii

Macadamia felted coccid, Eriococcus ironsidei (Williams) (Hemiptera: Eriococcidae) was first found infesting macadamia trees in the island of Hawaii in 2005. Macadamia felted coccid infests all above-ground parts of trees to feed and reproduce. Their feeding activity distorts and stunts new growth which causes yellow spotting on older leaves, and when population densities become high, branch dieback occurs. Different predatory beetles have been observed in macadamia nut trees infested by E. ironsidei, the most abundant were Halmus chalybeus, Curinus coeruleus, Scymnodes lividigaster, Rhyzobius forestieri, and Sticholotis ruficeps. To verify predation of E. ironsidei by these beetles, a molecular assay was developed utilizing species-specific primers to determine presence in gut content of predators. Using these primers for PCR analysis, wild predator beetles were screened for the presence of E. ironsidei DNA. Analysis of beetles collected from macadamia orchards revealed predation by H. chalybeus, C. coeruleus, S. lividigaster, R. forestieri, and S. ruficeps on E. ironsidei. This study demonstrates that these beetles may play an important role in controlling the population of E. ironsidei, and these predators may be useful as biocontrol agents for E. ironsidei.