A new repellent for redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae), a primary vector of the mycopathogen that causes laurel wilt

Authors: Cloonan, Kevin; Montgomery, Wayne; Narvaez, Teresa; Kendra, Paul

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2023
Publication Date: 6/21/2023
Citation: Cloonan, K.R., Montgomery, W.S., Narvaez, T.I., Kendra, P.E. 2023. A new repellent for redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae), a primary vector of the mycopathogen that causes laurel wilt. Plants. 12(13):2406. https://doi.org/10.3390/plants12132406.
DOI: https://doi.org/10.3390/plants12132406

Interpretive Summary: The redbay ambrosia beetle (RAB) is an exotic wood boring beetle that was first detected in Georgia in 2002. Adult females carry the spores of their fungal symbionts and inoculate host wood with fungi that then serve as a food source for adults and larvae. One of these fungal symbionts causes laurel wilt, a lethal disease of trees in the family Lauraceae including avocado, redbay, swampbay, and other tree species important to forest ecosystems. Since RAB’s introduction in 2002, native ambrosia beetle species have also acquired the fungal pathogen that causes laurel wilt and contributes to its’ spread. Laurel wilt and RAB have spread to 12 additional states, with few tools available to control the pathogen and beetle vectors. Thus, scientists from the USDA-ARS (Miami, FL) conducted a series of field tests in Miami-Dade and Broward Counties, FL, to examine the efficacy of piperitone as a repellent for RAB and native ambrosia beetle species as compared to the standard bark beetle repellent verbenone. All tests suggested that piperitone did not inhibit the attraction of native ambrosia beetles, but that piperitone and verbenone are effective repellents for RAB. The lower cost of piperitone compared to verbenone warrants further investigation of piperitone as a new repellent for potential incorporation into integrated pest management (IPM) programs for RAB. An effective, economic repellent for RAB provides a potential new tool for deterring beetle attacks and slowing the spread of laurel wilt.

Technical Abstract: Redbay ambrosia beetle, Xyleborus glabratus, was detected in Georgia, USA in 2002, and has since spread to 12 additional states. This wood-boring weevil carries a symbiotic fungus, Harringtonia lauricola, that causes laurel wilt, a lethal disease of trees in the Lauraceae. Native ambrosia beetles that breed in infected trees can acquire H. lauricola and contribute to the spread of laurel wilt. Since 2002, laurel wilt has devastated native Persea species in coastal forests and has killed an estimated 200,000 avocado trees in Florida. Since laurel wilt is difficult to manage once it has entered a susceptible agrosystem, this study evaluated piperitone as a candidate repellent to deter attacks by X. glabratus and other ambrosia beetles. Additionally, piperitone was compared to the known repellent verbenone as a potential cost effective alternative. Repellent efficacy was determined by comparing captures in traps baited with commercial beetle lures versus captures in traps baited with lures plus a repellent. In parallel 10-week field tests, addition of piperitone reduced captures of X. glabratus in a-copaene-baited traps by 90%; however, there was no significant reduction in captures of native ambrosia beetles in ethanol-baited traps. In two replicate 10-week comparative tests, piperitone and verbenone both reduced X. glabratus captures by 68-90%, with longevity the full 10 weeks. This study identifies piperitone as a new X. glabratus repellent with potential for pest management.