The impact of biocontrol agents on different chemotypes of Melaleuca quinquenervia, an invasive tree in south Florida

Authors: BLASKOWSKI, BLAKE - University Of South Florida; Tipping, Philip; MARTIN, MELISSA - University Of Florida; GETTYS, LYN - University Of Florida; Wheeler, Gregory; STILING, PETER - University Of South Florida; Smith, Melissa

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2026
Publication Date: 8/20/2026
Citation: Blaskowski, B., Tipping, P.W., Martin, M.R., Gettys, L., Wheeler, G.S., Stiling, P., Smith, M. 2026. The impact of biocontrol agents on different chemotypes of Melaleuca quinquenervia, an invasive tree in south Florida. Biological Control. 220. https://doi.org/10.1016/j.biocontrol.2026.106124.
DOI: https://doi.org/10.1016/j.biocontrol.2026.106124

Interpretive Summary: This investigation focuses on the interaction of chemotypes, which broadly correspond to ranges, and their herbivores. We found that flowering was reduced drastically in both chemotypes, but that biomass was significantly more impacted for the E-viridifloral chemotype - indicating that biological control may be more effective on these populations.

Technical Abstract: Across its natural and invaded range, Melaleuca quinquenervia, an invasive tree from Australia and Papua New Guinea, produces oils correspondent to two distinct chemotypes, based on production of essential oils. In Australia and Papua New Guinea, the two chemotypes separate geographically: Chemotype 1 occurs north of 25ºS and both chemotypes occur south of 25ºS. In south Florida, M. quinquenervia also occurs in two different habitats, dry and sandy soils in the west and wetter organic soils in the east. We investigated the effects of two biological control agents, the leaf feeding melaleuca snout weevil (Oxyops vitiosa), and the sap-sucking psyllid (Boreioglycaspis melaleucae) on both chemotypes in both types of habitats. We designed a common garden experiment to investigate the effects of herbivory and irrigation on M. quinquenervia growth with no difference in biological control agent abundance between chemotypes. The E-nerolidol chemotype (chemotype 1) grew significantly faster than the E-viridiflorol chemotype (chemotype 2), regardless of herbivory exposure. Seed production in plants exposed to herbivory was reduced by more than 99% compared to plants with limited herbivory, regardless of chemotype. The final height of insecticide-treated plants was over double that of unsprayed plants and the final trunk biomass was five times greater. However, in our experiments the effects of insecticide on final plant height, final trunk biomass and final branch biomass were greater for E-viridiflorol than E-nerolidol, suggesting biological control may have a greater impact on E-viridiflorol trees. Increased irrigation did not affect herbivore numbers but did significantly increase final tree height and final branch weight, and for height this increase was greater for E-viridiflorol. While our research suggests biological control agents are effective against both chemotypes, they also show that impacts are affected by both chemotype and environment. Acacia auriculiformis is part of the large genus Acacia within the Mimosoid clade of Fabaceae. The development and accessibility of modern genetic analyses have led to extensive revision in Acacia and Fabaceae in general. Acacia now comprises over 1000 species, and the genus is more narrowly geographically and taxonomically defined and are largely restricted to Australia (sensu (Koenen et al., 2020). The only Acacia taxon that is native to the United States is Acacia koa A. Gray, a Hawaiian endemic. All North American species that were included in Acacia sensu lato have been attributed to other genera including Senegalia, Acaciella, and Vachellia among others. Although a biological control release has never been conducted for A. auriculiformis, several species of invasive Acacia in South Africa provide successful examples of the use of classical biological control using herbivores and pathogens. The introduction of Calomela intemerata Lea (Chrysomelidae: Coleoptera) would represent the first biological control release of A. auriculiformis in the United States and Florida. This folivorous herbivore is needed as part of an integrated management approach to slow and halt the spread of A. auriculiformis northward and into more sensitive environments. Herein, we present the findings of a comprehensive host range test that reveals that C. intemerata maintains an extremely tight host relationship with A. auriculiformis. In no-choice tests, we observed no adult test feeding and no development on any native North American species. The only species for which we observed any non-target test feeding accompanied with development was Acacia cultriformis A. Cunn ex G. Don., an Australian congener that is used in horticultural applications in California. Development only occurred for 1 larva out of 100 larvae tested on the species. Only 30% of adults survived for 30 days on A. cultriformis and no eggs we