68 RESULTS The one-way ANOVA revealed that treatment was a significant predictor of GS density (F5,48 = 11.52, P < 0.0001). The post-hoc Dunnett’s test revealed the dinotefuran, pyriproxyfen plus oil, and flupyradifu- rone T1 and flupyradifurone T3 were treatments were significantly different (i.e., lower GS density) from the control treatment (Figure 1; Table 2). Of these 3 most efficacious treatments, trees treated with dinotefuran had the lowest GS densities. The flupyradifurone T2 the least efficacious and were not statistically differ- entiable from untreated controls. See Table 2 for sum- mary statistics. The average number of live GS adults on control- treated trees was 1.19/mm branch. In agricultural sys- tems, a “satisfactory” level of suppression is generally considered 80% reduction of a pest. Therefore, the “satisfactory” threshold of residual live GS for this study based on the control treatment (mean of 1.19) is 0.24. Dinotefuran was well below this threshold with a mean of 0.07 GS adults/mm branch. Both pyriproxy- fen plus horticultural oil and flupyradifurone T1 were just above this threshold at 0.26 GS adults/mm branch (78% suppression) and 0.34 GS adults/mm branch (71% suppression), respectively (Figure 1). DISCUSSION Red maple is one of the most popular tree species for planting in the urban landscape in North America. Its widespread use in these stressful environments can lead to major health concerns. Likely, the most wide- spread and damaging pests of ornamental and land- scape red maples in the southeastern and mid-Atlantic US is GS, often requiring intervention with insecti- cidal products. Consistent with current recommenda- tions by several state extension services, we found that dinotefuran and pyriproxyfen plus horticultural oil can reasonably be considered effective treatments for GS management when applied during crawler activity. Additionally, flupyradifurone may be consid- ered to be an efficacious treatment if applied during crawler activity. While we found that treatments of flupyradifurone applied post-crawler period were ineffective, we did not test any product prior to crawler emergence, which should be considered in future trials. Of the 3 products tested at the time of crawler emergence, dinotefuran was the most consistently efficacious, with a 96% reduction in GS density ©2021 International Society of Arboriculture Chase et al: Gloomy Scale Management relative to controls and the smallest 95% confidence interval of all treatments. These data certainly align with recommendations from extension services for the use of products containing this active ingredient. The systemic nature and application method options (usually foliar-, soil-, and bark-applied) for dinotefuran- containing products make these particularly attractive for GS management. Also, the longer expected resid- ual of soil- and bark-applied dinotefuran covering the extended GS crawler emergence/activity period may explain why this product had the lowest number of alive adults. While not strictly reaching the 80% reduction mark, pyriproxyfen plus horticultural oil was still found to have adequate levels of GS density reduction (78%). This treatment appeared to suffer from greater amount of variation in efficacy than dinotefuran when consid- ering standard deviation, standard error, 95% confi- dence intervals, and the range of densities counted (minimum and maximum values; Table 2). This com- bination of products relies heavily on (1) appropriate timing of application and (2) adequate coverage on the tree, as the insecticidal activity of these products requires contact. While these are disadvantages of this particular treatment, these products are generally considered environmentally friendly. Flupyradifurone, while also technically not achiev- ing the 80% reduction mark, can be considered effec- tive at suppressing GS crawlers when they were active, but was not effective when scale crawlers had settled. Flupyradifurone is favorable because the product is deemed “bee safe” (Glaberman and White 2014) and can be applied to flowering plants in accor- dance with the label. However, some studies have found that acute exposure to high doses impairs bee cognition, taste, and olfactory learning (Tan et al. 2017; Hesselbach and Scheiner 2018). Mixing flupyradifurone with triazole fungicides also increases bee toxicity and should never be practiced (Bayer Crop Science AG 2013; Tosi and Nieh 2019). Fur- thermore, despite some visitation by early-season pollinators (e.g., Batra 1985), red maple is considered to be a primarily wind-pollinated species and flowers very early in the season. The application of products for GS management should occur post-flowering, further limiting pollinator exposure. We found active and settled crawlers on 29 May when 1352.5 growing degree days (GDD)(base 50 °F/10 °C) had accumulated according to GreenCast®
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