Evaluation of organic, food-grade hydrophobic coatings for suppressing oviposition and increasing mortality of western cherry fruit fly (Diptera: Tephritidae)

Authors: Yee, Wee; KAISER, CLIVE - LINCOLN UNIVERSITY - NEW ZEALAND

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2022
Publication Date: 5/24/2022
Citation: Yee, W.L., Kaiser, C. 2022. Evaluation of organic, food-grade hydrophobic coatings for suppressing oviposition and increasing mortality of western cherry fruit fly (Diptera: Tephritidae). Environmental Entomology. https://doi.org/10.1093/ee/nvac033.
DOI: https://doi.org/10.1093/ee/nvac033

Interpretive Summary: In the Pacific Northwest of the USA, western cherry fruit fly is a quarantine pest of cherry. The fly is controlled using insecticides, but newer methods for control would help reduce insecticide input into the environment. One such method is the use of organic coatings sprayed on cherries to prevent or reduce egg laying by the fly into the fruit. Personnel at the USDA Temperate Tree Fruit & Vegetable Research Laboratory in Wapato, WA and Oregon State University and Lincoln University in New Zealand determined the effects of organic, food-grade coatings on reducing egg laying by flies in cherries in the laboratory and field. It was found that the coatings reduced egg laying by >90% versus controls in the laboratory and reduced larval infestations by >90% in the field. Results are important in that they identify an organic product that could potentially be used for fly control while reducing the need for extensive insecticide use

Technical Abstract: Newer non-toxic methods for protecting fruit from tephritid fruit fly attack are needed to reduce extensive insecticide use. Here, we evaluated organic, food-grade hydrophobic coatings that help protect sweet cherries (Prunus avium L.) from water loss and water-induced cracking for suppressing attack on cherries by western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephtitidae), as well as for their effects on fly mortality. Six formulations of coatings called PBCs that form elastic barriers on cherries and that consist of palm oil, safflower oil, microcrystalline cellulose, hemicellulose, and other components were tested. In the laboratory, 78.3% of flies that stung fruit slipped on PBC-coated cherry surfaces. In addition, fly visits on and oviposition in PBC-coated cherries were 66.1–93.5% and 59.1–99.5% lower, respectively, than in controls, suggesting both physical and visual or olfactory factors caused reductions in oviposition. In addition, mortality of females exposed to cherries coated with various PBC formulations (4.0–63.3%) was greater than in controls (0–8.5%). In 2020 and 2021, three sprays of PBC formulations were made on sweet cherry trees in field trials. In 2020 when fly densities were high, PBCs reduced larval infestations by 31.8% and 32.1%. In 2021 when fly densities were lower, PBCs reduced infestations by 86.8% and 90.5%, but sprays also reduced cherry size and glossiness. PBCs show promise in helping protect sweet cherry from attack by R. indifferens, although further testing is needed to improve PBC formulations so that they suppress fly oviposition without affecting cherry quality