Insights on the symbiotic associations of the tea shot hole borer (Coleoptera: Curculionidae)

Authors: CRUZ, LUISA - University Of Florida; MENOCAL, OCTAVIO - University Of Florida; Dunlap, Christopher; Cooperband, Miriam; Cloonan, Kevin; Tabanca, Nurhayat; CARRILLO, DANIEL - University Of Florida

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2025
Publication Date: 6/10/2025
Citation: Cruz, L.F., Menocal, O., Dunlap, C.A., Cooperband, M.F., Cloonan, K.R., Tabanca, N., Carrillo, D. 2025. Insights on the symbiotic associations of the tea shot hole borer (Coleoptera: Curculionidae). Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2025.1589710.
DOI: https://doi.org/10.3389/fmicb.2025.1589710

Interpretive Summary: The tea shot hole borer (TSHB) is an invasive ambrosia beetle that vectors Fusarium dieback, a vascular disease of avocado trees caused by the beetle's fungal symbionts. TSHB females carry multiple fungal species and it is not known which fungi are used as a food source and which ones produce the disease. To address these questions, scientists from the University of Florida, ARS, and APHIS conducted research with lab colonies of TSHB and pure cultures of six different symbionts (Fusarium sp. nov., Fusarium sp. AF-8, Fusarium sp. AF-6, Graphium sp., Acremonium sp., and Acremonium murorum). Results indicated that larvae were not able to develop into adults when fed only Acremonium sp. All the other symbionts provided sufficient nutrition; however, optimal development and reproduction were observed with Fusarium sp. nov. and AF-8. These two symbionts were also responsible for causing the most extensive disease lesions in infested avocado trees. This study provides a better understanding of the functional roles of each symbiont as well as their pathogenicity. This information may facilitate development of improved management strategies for Fusarium dieback and its insect vector.

Technical Abstract: The tea shot hole borer (TSHB), Euwallacea perbrevis (Schedl 1951) (Coleoptera: Curculionidae) is an invasive ambrosia beetle that vectors Fusarium fungi to avocado (Persea americana Mill.) in Florida. This study investigates the role of Fusarium sp. nov., Fusarium sp. AF-8, Fusarium sp. AF-6, Graphium sp., Acremonium sp., and Acremonium murorum as nutritional symbionts of TSHB, and the role of Fusarium spp. in disease development. Four experimental approaches were used: i) Larval feeding assays on individual symbiont cultures, ii) Rearing of TSHB on avocado sawdust substrate inoculated with individual symbionts, iii) Production of TSHB colonies carrying a single species of Fusarium, here referred to as Mono-Fusarium Lines (MFL), and iv) Infestation of avocado with the MFL. More adult females were obtained from larvae fed on Fusarium sp. nov., and AF-8, and no individuals reached adulthood feeding on Acremonium sp. Reproduction decreased when TSHB developed on substrates pre-inoculated by AF-6 and AF-8. In addition, Fusarium sp. nov., and AF-8 were the only two symbionts that always persisted in TSHB mycangia after breeding for two generations on substrates pre-inoculated with other symbionts. TSHB developed and reproduced feeding individually on all Fusarium spp. but the total brood and number of females were significantly smaller in AF-6 than in the other MFL and the regular laboratory colony used as the control. The greatest number and most extensive lesions on avocado branches were caused by Fusarium sp. nov. and AF-8 MFL. These results indicate that Fusarium sp. nov. and AF-8 play a key role as a food source for this beetle species.