Arboriculture & Urban Forestry 46(5): September 2020 water. Four injection points were made into each tree near the root collar, spacing them about equally apart. The average dose of active ingredient (AI) injected was 4.8 g of EB per tree. Experiment 2 Trees in experiment 2 were treated on 5 November 2009. Ten trees were injected with TREE-äge using the QUIK jet micro-injector (Arborjet, Inc.) and ten trees were set aside as untreated controls. The QUIK- jet micro-injector is designed with a 5-cc capacity barrel and applied at one point at a time. This micro-injection method made it possible to increase the number of injection points around the tree, but at a lower per tree dose. Study trees (n = 20) averaged 28.8 ± 2.0 cm (mean ± 1 SD) DBH. Those treated with TREE-äge (n = 10; mean DBH = 28.4 ± 2.0 cm) were injected with 7.5 mL of product per 2.5 cm DBH, a rate inter- mediate to the medium and high label use rates. To promote better distribution of insecticide across the phloem tissue, injections were made about every 9 cm of circumference at the root collar (mean number of sites = 11.4 per tree). The average dose of AI was 3.4 g of EB per tree. Experiment 3 Trees in experiment 3 were treated on 11 June 2013. Ten trees each were treated with (a) TREE-äge using the air-hydraulic micro-injector (Arborjet, Inc.) plus GLV/verbenone (Synergy Semiochemicals, Corp., Burnaby, BC, Canada; Product No. 3413), the latter to deter beetle attack; (b) TREE-äge and Alamo (14.3% wt/wt propiconazole, ME Syngenta Crop Protection, Greensboro, NC, USA)(PPZ); or (c) were 335 untreated controls. The study trees (n = 30) averaged 25.6 ± 2.5 cm DBH. TREE-äge was applied once every 10 cm of basal circumference at 6.7 mL per injection (equivalent to the medium label rate of 5 mL per 2.5 cm DBH) in treatments (a) and (b). In addi- tion, treatment (a) received one pouch each of verbe- none and GLV affixed on the north-facing bole at 182 cm from ground level. In addition, treatment (b) received PPZ at 8 mL per injection site (label rate of 6 mL PPZ per 2.5 cm DBH). The mean cm DBH of injected trees and number of injection points were 26.0 cm and 10, respectively. The mean dosages of EB and PPZ were 2.08 g and 8.8 g, respectively. Table 1 provides a summary of the three experiments. Beetle Challenge Challenge from MPB was promoted in the experi- ments using commercially available attractant lures consisting of exo-brevicomin, trans-verbenol, and a 1:1 mixture of myrcene and terpinolene (Synergy Semiochemicals, Corp., Burnaby, BC, Canada; Prod- uct No. 3093). This is the combination lure identified as most attractive for MPB in northeastern California (Strom et al. 2004). Attractant lures were attached to poles approximately 1 m away from the tree bole at 1.2-m height (Strom et al. 2004) and installed once roads were passable during the early flight season for MPB in the study area. In experiment 1, lures were deployed on 1 July 2008, replaced on 1 August 2008, and removed on 4 September 2008. In experiment 2, trees were baited with attractant lures on 7 July 2010, and lures were removed on 4 November 2010. In experiment 3, trees were baited 11 July 2013 through 21 May 2014, with lures attached to a stake 1 m from Table 1. Summary of experiments 1–3 reflects the modification of protocols over time. In the first experiment, TREE-äge was injected into Pinus monticola (western white pine) using the Tree I.V. at relatively wide spacing at the 10 mL/2.5 cm label rate. Subsequent experiments used the modified closer injection spacing using as low as the 5 mL/2.5 cm label rate. In the last experiment, either verbenone and green leaf volatile (V/GLV) or 14.3% propiconazole (PPZ), a systemic fungicide, was applied in conjunction with TREE-äge. Treatment date 5 November 2009 11 June 2013 Treatment 17-18 September 2007 TREE-äge Control TREE-äge Control Reps Avg. cm DBH 10 10 10 10 TREE-äge/V/GLV 10 TREE-äge/PPZ Control 10 10 30.9 ± 2.0 cm 30.9 ± 2.0 cm 28.4 ± 2.0 cm 28.8 ± 2.0 cm 25.6 ± 2.5 cm 25.6 ± 2.5 cm 25.6 ± 2.5 cm Method Tree I.V. QUIK-jet Air-hydraulic Air-hydraulic Dose/2.5 cm DBH 10 mL 7.5 mL 5.0 mL 5.0 /6.0 mL No. injects 4 11.4 10.2 10.2 mL/tree 126 86 52 52/61.4 ©2020 International Society of Arboriculture
September 2020
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