Document Type

Article

Publication Date

1-1-2018

Abstract

Root-feeding beetles, including several species of Hylastes Erichson (Coleoptera: Curculionidae), Hylurgops LeConte (Coleoptera: Curculionidae), Hylobius Gemar (Coleoptera: Curculionidae), Pachylobius LeConte (Coleoptera: Curculionidae), Pissodes Germar (Coleoptera: Curculionidae), and Steremnius Schönherr (Coleoptera: Curculionidae), have emerged as serious problems in conifer plantations and forests in the United States and Canada in recent decades. Root-feeding beetles are particularly associated with stressed, diseased, or injured trees. Emerging adults kill seedlings by girdling them at the root collar and kill older trees, at least in the North and West, by transmitting fungal root pathogens in the genus Leptographium Lagerberg & Melin (Ophiostomatales: Ophiostomataceae). In the South seedling, mortality can be as high as 60% for seedlings planted in winter following fall harvest. For stands harvested after 1 July, planting should be delayed a full year. Broadcast insecticides can be used, but dipping seedlings in 0.75% permethrin prior to planting and physical barriers to feeding have proven effective. However, an integrated pest management approach that emphasizes a combination of measures to minimize attraction of beetles and to maintain health of host trees is recommended. Shelterwood harvest and soil scarification can create site conditions that minimize attraction of root beetles. Precommercial thinning and prescribed fire are often used to reduce tree competition and reduce vulnerability to stem-colonizing bark beetles. However, root beetles are attracted to thinned or burned stands, for at least 6-7 mo. Therefore, thinning should be avoided in areas of high risk for root disease transmission or, when necessary, thinning should be implemented during June or July following beetle dispersal in May. Semiochemicals can be used to monitor abundances of root beetles.

Publication Source (Journal or Book title)

Journal of Integrated Pest Management

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