Entomopathogenic fungi and chemical insecticides have synergistic action against adult large pine weevil, Hylobius abietis

van Vlaenderen, J, Hennessy, N, O’Tuama, P, Williams, CD ORCID: 0000-0003-0528-3436 and Griffin, CT (2025) Entomopathogenic fungi and chemical insecticides have synergistic action against adult large pine weevil, Hylobius abietis. Biological Control, 212. p. 105945. ISSN 1049-9644

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Abstract

The large pine weevil, Hylobius abietis, is a serious pest of reforestation across much of northern Europe. Larvae develop in the stumps and roots of recently felled conifers, and adults feed on the bark of young trees used to replant the site. Entomopathogenic fungi and chemical insecticides, alone and in combination, were tested against adult pine weevil in laboratory and field experiments. In a broad screening experiment, weevils were dipped in conidial suspension of Beauveria bassiana (Bb Naturalis and Bb SC4), Beauveria caledonica (Bc SG61) and Metarhizium anisopliae (Ma F52 and Ma SG6) and/or provided with twigs treated with chemical insecticides (cypermethrin, acetamiprid and thiacloprid). When assessed after 14 or 17 days, there was higher weevil mortality in combined treatments than expected based on individual treatments, with synergistic effects demonstrated in most cases. In a second laboratory experiment, Bb Naturalis, Bc SG61 and Ma F52 applied in each of two ways, either by dipping weevils or contaminating the substrate, gave synergistic effects in combination with cypermethrin, and mainly additive effects with acetamiprid. Weevil cadavers in all fungus- insecticide treatments tested developed mycosis, which would facilitate recycling of fungi in the field. In a f ield trial, a commercial formulation of Ma F52 (Met52) and cypermethrin were tested alone and in combination for protection of young Sitka spruce trees. Weevil feeding damage on trees treated with Met52 and half the recommended rate of cypermethrin did not differ significantly from that of trees that received full rate cypermethrin, but damage to trees that received half rate cypermethrin was higher. This study demonstrates the potential of entomopathogenic fungi to reduce the amount of chemical insecticide used to protect trees against pine weevil damage as part of an integrated pest management approach to pine weevil.

Item Type:	Article
Uncontrolled Keywords:	0608 Zoology; Entomology; 3109 Zoology
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QH Natural history > QH301 Biology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Elsevier BV
Date of acceptance:	10 December 2025
Date of first compliant Open Access:	19 December 2025
Date Deposited:	19 Dec 2025 15:09
Last Modified:	19 Dec 2025 15:09
DOI or ID number:	10.1016/j.biocontrol.2025.105945
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27749

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