Effects of laboratory grade limonene and a commercial limonene-based insecticide on Haematobia irritans irritans (L.) (Muscidae: Diptera): deterrence, mortality, and reproduction

Authors: Showler, Allan; Harlien, Jessica; Perez De Leon, Adalberto - Beto

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2019
Publication Date: 3/6/2019
Citation: Showler, A., Harlien, J.L., Perez De Leon, A.A. 2019. Effects of laboratory grade limonene and a commercial limonene-based insecticide on Haematobia irritans irritans (L.) (Muscidae: Diptera): deterrence, mortality, and reproduction. Journal of Medical Entomology. 56(4):1064-1070. https://doi.org/10.1093/jme/tjz020.
DOI: https://doi.org/10.1093/jme/tjz020

Interpretive Summary: Horn flies are economically important parasites of cattle worldwide that have acquired resistance to many conventional insecticides. We assessed laboratory grade limonene, a botanical compound, and a commercial limonene-based product, Orange Guard, for bioactivity against horn flies in terms of contact toxicity on eggs, adults, larval and pupal development, and repellence, and sublethal and fumigation effects. Egg viability in response to contact declined in response to laboratory grade limonene and Orange Guard. Contact with adult horn flies caused substantial knockdown (immobilization) in response to both limonene formulations that lasted throughout the 4 h bioassay. While direct contact of laboratory grade limonene caused substantial mortality, mortality was negligible in response to Orange Guard. Each of the two treatments attracted adult horn flies at concentrations <0.1%. Sublethal concentrations on adult female horn flies did not reduce the numbers of eggs produced, but 5.8% limonene concentration reduced egg hatchability.

Technical Abstract: The horn fly, Haematobia irritans irritans (L.), is an economically important and cosmopolitan blood feeding ectoparasite of cattle. Resistance to conventional insecticides is increasingly problematic and alternative pesticides, including botanical natural products, are being researched. Limonene is a cyclic monoterpene repellent to some insects that occurs in the rinds of citrus fruits and other plants. We assessed laboratory grade limonene and a commercial limonene-based product, Orange Guard, for bioactivity against H. irritans irritans in terms of contact effects on egg mortality, adults, larval and pupal development, repellence, and sublethal and fumigation effects. Egg viability in response to contact declined when Orange Guard was tested at 1.45%, 2.9%, and 5.8% whereas laboratory grade limonene concentrations of 5.8% and 11.6% showed ovicidal effect. Contact with adult H. irritans irritans caused substantial knockdown (immobilization) in response to 5.8% laboratory grade limonene and 2.9% Orange Guard. The knockdown effect lasted throughout the 4 h bioassay, but higher concentrations of laboratory grade limonene and Orange Guard resulted in less, and often shorter periods of knockdown. While direct contact of laboratory grade limonene caused substantial mortality at the 2.9% and 5.8% concentrations, mortality was negligible even when the flies were sprayed with undiluted Orange Guard containing 5.8% limonene. Laboratory grade limonene and Orange Guard attracted adult H. irritans irritans even at concentrations <0.1%. Sublethal concentrations on adult female H. irritans irritans did not reduce the numbers of eggs produced, but the 5.8% concentration reduced egg hatchability. We suggest that the attractancy of limonene might be useful for trapping H., irritans irritans adults.