A 2-component blend of coconut oil-derived fatty acids as an oviposition deterrent against Drosophila suzukii (Drosophilidae: Diptera).

Coconut free fatty acid (CFFA), a mixture of 8 fatty acids derived from coconut oil, is an effective repellent and deterrent against a broad array of hematophagous insects. In this study, we evaluated the oviposition deterrent activity of CFFA on spotted-wing drosophila (SWD; Drosophila suzukii), a destructive invasive pest of berries and cherries, and identified bioactive key-deterrent compounds. In laboratory 2-choice tests, CFFA deterred SWD oviposition in a dose-dependent manner with the greatest reduction (99%) observed at a 20-mg dose compared with solvent control. In a field test, raspberries treated with 20-mg CFFA received 64% fewer SWD eggs than raspberries treated with the solvent control. In subsequent laboratory bioassays, 2 of CFFA components, caprylic and capric acids, significantly reduced SWD oviposition by themselves, while 6 other components had no effect. In choice and no-choice assays, we found that a blend of caprylic acid and capric acid, at equivalent concentrations and ratio as in CFFA, was as effective as CFFA, while caprylic acid or capric acid individually were not as effective as the 2-component blend or CFFA at equivalent concentrations, indicating the 2 compounds as the key oviposition deterrent components for SWD. The blend was also as effective as CFFA for other nontarget drosophilid species in the field. Given that CFFA compounds are generally regarded as safe for humans, CFFA and its bioactive components have potential application in sustainably reducing SWD damage in commercial fruit operations, thereby reducing the sole reliance on insecticides.

Coconut oil derived five-component synthetic oviposition deterrent for oriental fruit fly, Bactrocera dorsalis.

BACKGROUND: Bactrocera dorsalis, oriental fruit fly (OFF), is one of the most destructive agricultural pests. Although bait sprays can effectively control OFF, resistance development has been a concern. We evaluated the oviposition deterrent activity of coconut free fatty acids (CFFA), a mixture of eight coconut oil-derived fatty acids known to repel hematophagous insects and deter their feeding and oviposition, against OFF females. RESULTS: In laboratory 72-h two-choice assays using guava-juice infused-agar as an oviposition substrate, CFFA deterred OFF oviposition in a dose-dependent manner with the greatest reduction of 87% at 20 mg dose compared to the control. When the eight CFFA components were tested individually, four compounds (caprylic, capric, oleic, and linoleic acids) significantly reduced OFF oviposition ('negative-compounds'), two (lauric and myristic acids) had no effect ('neutral-compounds'), and two (palmitic and stearic acids) stimulated OFF oviposition ('positive-compounds'). In two-choice tests, the 'negative-compounds' blend failed to elicit the same level of oviposition reduction as CFFA at equivalent concentrations found in CFFA. Adding the two 'neutral-compounds' recovered the oviposition deterrence similar to CFFA. Subsequent subtraction tests showed that four 'negative-compounds' plus lauric acid was as effective as CFFA in reducing OFF oviposition in guava-juice agar. This five-component key-deterrent blend also reduced OFF oviposition by 95 and 72% on papaya and tomato fruit, respectively. CONCLUSION: CFFA acts as an oviposition deterrent for OFF. Given that CFFA compounds are generally regarded as safe for humans and the environment, CFFA and its bioactive components have potential use in behavioral control strategies against OFF. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.