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Published VersionCC BY-NC-ND V4.0, Open Access
Journal article
Did a cryptogenic nematode strain control a sirex wood wasp outbreak?
Australian Forestry, Vol.88(4), pp.178-187
2025
Abstract
Sirex noctilio (sirex) is a significant pest of Pinus plantations in the Southern Hemisphere. Biological control and stand management to reduce tree stress (e.g. thinning) are effective in managing sirex in commercial plantations, but the relative contribution of each of these in controlling a sirex outbreak is untested. In this study we attempt to disentangle the relative roles of 'top-down' (natural enemies) and 'bottom-up' (susceptible host tree availability) forces in regulating a sirex outbreak. We monitored a sirex outbreak in an unthinned Pinus radiata plantation in New South Wales to determine whether biological control alone could effectively reduce the sirex population. The plantation was 11 years old in 2015 when sirex attack was first detected and had very high stocking (3000-6500 s.p.h.) due to ineffective pine wildling control. Inoculation of naturally struck trees with the Kamona strain of the nematode Deladenus siricidicola began in 2016, with a total of 16 million nematodes inoculated up to 2019. By 2020, the outbreak had subsided with only a few sirex-attacked trees detected. Ground plots revealed that 40% of trees were struck by sirex and that suppressed trees and wildings were by far the most susceptible. The number of susceptible trees had significantly reduced by 2020, likely contributing to sirex control via reduced host availability, but there were still a substantial number of susceptible trees in the stand due to the large number of wildings. The wasp Ibalia leucospoides parasitised approximately 30% of sirex larvae, also contributing to control. Nematode parasitism increased steadily from <5% at the start of the outbreak to 95% of emerging female sirex being parasitised by 2019. This suggests successful anthropogenic intervention via inoculative biological control with Kamona nematodes played a major role in controlling the sirex outbreak. However, molecular examination of nematodes from emerging sirex revealed that none were Kamona; all were the newly discovered Lineage D strain. Thus, biocontrol of sirex with nematodes was primarily via adventive classical biocontrol, not inoculative biocontrol. The implications of this are discussed.
Details
- Title
- Did a cryptogenic nematode strain control a sirex wood wasp outbreak?
- Authors
- A. J. Carnegie (Corresponding Author) - New South Wales Department of Primary IndustriesM. Nagel - New South Wales Department of Primary IndustriesD. Sargeant - New South Wales Department of Primary IndustriesK. N. E. Fitza - University of PretoriaH. F. Nahrung - University of the Sunshine Coast
- Publication details
- Australian Forestry, Vol.88(4), pp.178-187
- Publisher
- Taylor & Francis Australasia
- Date published
- 2025
- DOI
- 10.1080/00049158.2026.2627706
- ISSN
- 2325-6087
- Copyright note
- © 2026 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent
- Grants
- Sirex in Queensland (2012-14 seasons), 0980022258, National Sirex Coordination CommitteeBiological invasions in forestry: drivers, predictors and mitigation for biosecurity and industry, 0980025646, Advance Queensland (Australia, Brisbane)
- Organisation Unit
- Forest Industries Research Centre
- Language
- English
- Record Identifier
- 991216249902621
- Output Type
- Journal article
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