90 However, Strom et al.: Evaluating Insecticides for Preventing Southern Pine Beetles the uncertainty of achieving successful application (i.e., sufficient movement to phloem), particularly by soil drench, along with the ready availability and lower cost of imidacloprid products (relative to Safari), led researchers to include imi- dacloprid in this evaluation, but not dinotefuran. The wide availability of these products and their ease of application make them an obvious choice by do-it-yourself homeowners for use against SPB. As mentioned, the primary objective of this study was to assess the effects of general-use insecticides prophylactically applied to pine hosts against New Jersey SPB. Four products were eval- uated using a series of small-bolt trials (Strom and Roton 2009; Strom and Roton 2011): Onyx (23.4% bifenthrin; FMC Corp., Philadelphia, Pennsylvania, U.S.), Astro (36.8% permethrin; FMC Corp., Philadelphia, Pennsylvania, U.S.), Martin’s Dominion Tree & Shrub (hereafter Dominion; 1.47% imidacloprid, Control Solu- tions, Inc., Pasadena, Texas, U.S.), and Xytect 2F (hereafter Xytect; 21.4% imidacloprid; Rainbow Treecare Scientific Advancements, Minnetonka, Minnesota, U.S.). All are labeled for application against bark beetles and none was considered restricted use in New Jersey at the time of the study. Dominion is a generic product, similar to Bayer Advanced™ Tree & Shrub, while Xytect was of interest because its label allowed an application rate of twice as much AI. Both were applied as soil drenches, while Onyx and Astro were applied as bole sprays. With facilities and staff in Louisiana, U.S., and previously developed methods for such research, the study authors addressed research objectives by treating trees in central Louisiana and challenging them with SPB from New Jersey and Mississippi, U.S. Researchers also challenged treatments with Ips avulsus, because this species provides reliable pressures in areas of Louisi- ana, and to extend results to this typically less severe but oftentimes more present pest of pines. MATERIALS AND METHODS Application of Tree Protection Treatments Thirty loblolly pines (average DBH = 11.4 cm) were selected in central Louisiana for this study. Each tree received one of five randomly assigned ©2015 International Society of Arboriculture treatments: untreated control, Astro, Onyx, Do- minion, or Xytect. Treatments were applied on March 14, 2012, using the maximum label rate of each product. This resulted in an average per tree application rate of 12 ml (~2.6 ml AI) / 2.5 cm DBH for Xytect, and 90.3 ml (~1.3 ml AI) / 2.5 cm DBH for Dominion. For consistency of application between products in the experimental design, researchers adjusted label instructions for treatment with imidacloprid products. Ap- plication of soil drenches was made in 3.79 L of tap water to each tree and maximum label rates were used (per DBH cm) regardless of tree DBH. Raking around the base of each tree provided a mineral soil surface and a raised barrier of litter detritus to help eliminate product movement from the target area. Bole sprays were applied to a maximum height of 2.5 m using a handheld garden sprayer (Ace Hardware model number 7215064). Label rates for bark beetles were fol- lowed for Onyx (2 pt / 100 gal) and Astro (5.35 qt / 100 gal), providing a mixed product with 0.06% AI (bifenthrin) for Onyx and 0.5% AI (perme- thrin) for Astro. Imidacloprid product labels sug- gest a 60-day minimum waiting period following soil drench applications to allow product uptake, so treatment time was selected to allow challenge by SPB beginning mid to late May 2012. At the appropriate time, trees were felled and bucked into small bolts (10–12 cm long) to allow products to be challenged by SPB in field and laboratory trials (Strom and Roton 2009; Strom and Roton 2011). Companion bolts from each tree were stripped of their phloem for determination of imidaclo- prid residue concentrations (Fischer et al. 2009). In 2011, similar trials in New Jersey were attempted but did not result in sufficient attacks of control bolts for a valid test of treatment effec- tiveness (Table 1). However, imidacloprid residue concentrations were determined from tree phloem tissue and are reported herein. Loblolly pines were treated on May 26, 2011, using appli- cation methods similar to 2012. In addition, drought conditions in 2011 forced researchers to apply 3.7 L of water per tree at one and five days aſter soil drench application. Trees were felled, bucked, and the phloem removed for residues on July 29, 2011 (64 days posttreatment) and August 24, 2011 (90 days posttreatment).
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