Deterrence and behavioral mode of coconut oil-derived free fatty acids on Zeugodacus cucurbitae oviposition

Authors: MOVVA, VIJAYA - University Of Hawaii; Zhu, Junwei; RODA, AMY - Animal And Plant Health Inspection Service (APHIS); Kendra, Paul; Yang, Xiangbing; Cloonan, Kevin; TAY, JIA-WEI - University Of Hawaii; Cha, Dong

Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2024
Publication Date: 11/3/2024
Citation: Movva, V., Zhu, J.J., Roda, A., Kendra, P.E., Yang, X., Cloonan, K.R., Tay, J., Cha, D.H. 2024. Deterrence and behavioral mode of coconut oil-derived free fatty acids on Zeugodacus cucurbitae oviposition. Insect Science. https://doi.org/10.1111/1744-7917.13460.
DOI: https://doi.org/10.1111/1744-7917.13460

Interpretive Summary: Melon fruit fly is one of most destructive invasive pests of fruits and vegetables worldwide. Although bait sprays can effectively control their damage, resistance development has been reported. Researchers at USDA-ARS, APHIS-PPQ, and University of Hawaii have identified a mixture of five coconut-oil derived fatty acids as novel oviposition deterrent for melon fly. In a series of bioassays, when directly applied on surface, the 5-component mixture significantly reduced melon oviposition in artificial oviposition substrate and real fruit. These compounds are generally regarded as safe and have great potential as a novel management tool to control melon fly damage in susceptible crops, providing melon management programs an alternative means to protect fruit and prepare for the undesirable event of establishment of these flies that can constitute as a serious trade-barrier.

Technical Abstract: Previous studies have reported oviposition deterring properties of coconut free fatty acid (CFFA) compounds on fruit flies with different key deterrent components identified for different species. In this study, we evaluated oviposition deterrence of eight CFFA compounds using laboratory two-choice bioassays against melon fly, Zeugodacus cucurbitae, determined key-bioactive deterrent compounds, and evaluated their behavioral mode. Unlike other reported fruit fly species, the CFFA mixture increased Z. cucurbitae oviposition at 20 mg dose compared to solvent control when directly applied on pumpkin agar as an oviposition substrate. When tested individually in subsequent tests, four compounds (caprylic, capric, oleic, and linoleic acids) significantly reduced the oviposition (‘negative-compounds’), one compound (stearic acid) had no effect (‘neutral- compound’), and three compounds (lauric, myristic, and palmitic acids) stimulated the oviposition (‘positive- compounds’). The 4-component negative-compound blend was effective at reducing oviposition, However, adding the neutral-compound to the 4-component blend (5-component blend, 5c) further reduced oviposition. In contrast adding any of the positive-compounds individually to the 5c increased oviposition, suggesting 5c as the key oviposition deterrent components for Z. cucurbitae. Oviposition deterrence to the 5c was also observed in no-choice assays and when the blend was applied to cucumbers. When given a choice over 24 h, Z. cucurbitae made 74.3% fewer visits, spent 69.8% less time, and oviposited 89.3% fewer eggs per min on the 5c treated agar than control agar. These behaviors suggest that the 5c blend has both spatial repellency and contact deterrence at the concentration tested in this study. Given that 5c compounds are registered food additives and generally regarded as safe, 5c has a potential use in behavioral control strategies against Z. cucurbitae.