Arboriculture & Urban Forestry 46(5): September 2020 Arboriculture & Urban Forestry 2020. 46(5):333–346 URBAN FORESTRY ARBORICULTURE Scientific Journal of the International Society of Arboriculture & Evaluation of Stem-Injected TREE-äge® (4% Emamectin Benzoate) for Protecting Western White Pines ( Beetle ( (Coleoptera: Curculionidae: Scolytinae) By Joseph J. Doccola, Sheri L. Smith, Joseph B. Fischer, and Brian L. Strom Abstract. The protection of high-value trees against bark beetles and the development of alternatives to bole sprays is a priority for the tree manager. The objective of this study was to evaluate stem-injected TREE-äge® (emamectin benzoate [EB]) as a protective treatment for west- ern white pines (Pinus monticola Dougl. ex D. Don) against mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins). Treatment effi- cacy was based solely on tree mortality as per Shea protocols (i.e., ≥ 60% check vs. ≤ 20% treated tree mortality). Our first experiment was installed in 2007 and included trees stem-injected with TREE-äge and untreated controls. Bole application of S-(-)-verbenone and green leaf volatile (GLV) blend was included for observational comparison. Pressure from MPB was heavy, as indicated by the number and timing of control tree mortality (90%). Strip attacks by MPB in TREE-äge trees indicated that the impacts of EB, and by inference its distribution, were inconsistent. In 2009, the injection protocol was revised to improve EB distribution in the phloem via closer injection points. In the 2009 TREE-äge-treated trees, adult beetle mining stopped when they contacted phloem and was insufficient to cause tree death by girdling. Blue-stain fungi colonized the sapwood of trees in both studies. Isolates from autopsied trees treated with TREE-äge alone were subsequently identified as Grosmannia clavigera and Leptographium longiclavatum (Ophiostomatales: Ascomycota), species that can incite tree mortality. In 2013, we revised our protocol to include GLV plus verbenone or propiconazole with TREE-äge, wherein these treatments proved effective in protecting trees against MPB and their associated pathogenic fungi. Keywords. Bark Beetles; Blue-Stain Fungi; Grosmannia clavigera; Leptographium longiclavatum; Propiconazole; Tree Injection; Verbenone. ) from Mountain Pine Hopkins) 333 INTRODUCTION White pines, including western white (Pinus monticola Dougl. ex D. Don), sugar (P. lambertiana Dougl.), limber (P. flexilis James), and whitebark (P. albicaulis Engelm.), are a component of more than 28 Society of American Foresters (SAF) Cover Types (Burns and Honkala 1990). They are important throughout the western USA for timber, aesthetics, recreation, water quality, and ecosystem functioning and are favored hosts for the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), the major insect threat to western white pines (Furniss and Carolin 1977; Burns and Honkala 1990). Effective treatments (i.e., as defined by Shea et al. 1984) for the protection of indi- vidual pines from MPB attack are limited to insecti- cides applied to the outside of the bole prior to beetle attack. Shea’s protocol is a management tool that defines treatment effectiveness under conditions where beetle pressures incite ≥ 60% of control tree mortal- ity, but cause ≤ 20% of treated tree mortality. Active ingredients (products) with demonstrated efficacy include carbaryl (Sevin™), which is often preferred due to its longevity (reliably two seasons), bifenthrin (Onyx™), and permethrin (Astro™), both of which typically provide one season of protection (Shea et al. 1984; Haverty et al. 1985; Fettig et al. 2006). If bole- sprayed insecticides are undesirable for a particular ©2020 International Society of Arboriculture Pinus monticola Dendr octonus ponder osae
September 2020
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