Laurel wilt is a vascular disease that has caused extensive mortality of trees and shrubs in the Lauraceae family, which include many commercially, ecologically and culturally important species such as Redbay, Persea borbonia. and avocado P. americana. Laurel wilt is caused by the fungus Raffaelea lauricola that is vectored by the exotic redbay ambrosia beetle, Xyleborus glabratus. We discovered that levels of methyl salicylate (MeSA) significantly increased in redbay three days post inoculation with R. lauricola, and that X. glabratus was significantly repelled by MeSA in olfactometer bioassays. These findings are consistent with observations that pioneer beetles abandon host trees shortly after attempting initial colonization. We decided to test MeSA in field condition, as well as verbenone, an anti-aggregation pheromone that has been found to repel a wide diversity of bark beetles. During the experiment conducted on cut redbay bolts, we observed a decrease in terms of arrivals to the bolts as well as number of boring holes found in the bolts at the end of the study for both MeSA and verbenone treatments. However, on subsequent experiments conducted on whole trees on a larger scale only verbenone significantly repelled redbay ambrosia beetles. In a final step, we included verbenone in a push-pull system in forest and avocado grove settings. In redbay, the attractant used was α-copaene a sesquiterpenes known to attract X. glabratus, while ethanol was used in avocado orchards. In both situations, we were able to significantly reduce the number of beetles attacking redbay and avocado. In redbay, we were able to reduce beetle populations by nine fold as compared with untreated controls.

Development of a push-pull system for the redbay ambrosia beetle Xyleborus glabratus, vector of the laurel wilt pathogen

2019 Fall National Meeting

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