Comparison of Ambrosia Beetle Communities in Two Hosts with Laurel Wilt: Swampbay vs. Avocado

The invasive redbay ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), is an exotic wood-boring pest first detected in 2002 near Savannah, Georgia.  The beetle’s dominant fungal symbiont, Raffaelea lauricola, is the pathogen that causes laurel wilt, a lethal disease of trees in the family Lauraceae. Currently established in eight states in the southeastern U.S., X. glabratus and laurel wilt are responsible for severe mortality of native Persea species, particularly redbay (P. borbonia) and swampbay (P. palustris).  Due to rapid southward spread, laurel wilt now threatens avocado (P. americana) in south Florida, but in contrast to the situation in bay forests, X. glabratus is detected at very low levels in affected groves.  There is evidence that avocado is a poor reproductive host for X. glabratus, and that R. lauricola can be transferred laterally to other species of ambrosia beetle that breed in infected trees.  To better understand the beetle communities in different ecosystems exhibiting laurel wilt, parallel field tests were conducted in an avocado grove in Miami-Dade County and a swampbay forest in Highlands County, FL.  Both sites contained a mixture of healthy trees and trees symptomatic for various stages of laurel wilt.  Treatments included ethanol lures (the best general attractant for ambrosia beetles) and essential oil lures (the best attractants for X. glabratus).  This presentation summarizes the numbers and diversity of ambrosia beetles captured in field tests, and compares the efficacy of lures for detection of X. glabratus, the primary vector of laurel wilt.