Studies on the biology, host specificity, and feeding behavior of Acythopeus cocciniae O'Brien and Pakaluk (Coleoptera: Curculionidae) on Coccinia grandis (L.) Voigt (Cucurbitaceae) and Zehneria guamensis (Merrill) Fosberg (Cucurbitaceae)

The invasive plant ivy gourd Coccinia grandis (L.) Voigt (Cucurbitaceae) first appeared on Guam in the 1980s and subsequently spread to about 200 ha in the absence of natural enemies. Following its successful introduction as a biological control agent in Hawaii, the weevil Acythopeus cocciniae O'Brien and Pakaluk (Coleoptera: Curculionidae) was brought to Guam under quarantine for host specificity testing against the endemic cucurbit, Zehneria guamensis (Merrill) Fosberg (Cucurbitaceae) and for further biological characterization. A. cocciniae preferred C. grandis over Z. guamensis in single- and two-host choice tests. No larval feeding was ever observed on Z. guamensis plants in two-host tests, and the single instance of A. cocciniae feeding on Z. guamensis in single-host tests was likely to avoid starvation. In 2004, A. cocciniae at the initial field release site in northern Guam dispersed primarily downwind in accordance to the prevailing northeasterly trade winds. However, only a single vine with a few adult weevils, larvae, and pupae were found at this site four years later in January 2008. This decrease was attributed to suppression by A. cocciniae. Since its initial release in 2004 A. cocciniae has established and dispersed throughout Guam.