Arboriculture & Urban Forestry 32(4): July 2006 139 except for individual shoot sprays were applied by an expe- rienced, ISA-certified arborist assisted by the authors. A non- ionic surfactant (Break-thru; Goldschmidt Chemical, Hopewell, VA) was added at 0.31 mL/L (4 oz/100 gal) to all spray mixes unless otherwise indicated. For data analyses, percentages were arsine-transformed, and scale counts were log-transformed as necessary to correct for heterogeneity of variance. Treatment effects were ana- lyzed by two- or one-way analysis of variance (ANOVA), depending on whether treatments were blocked, followed by Dunnett’s test ( 0.05) for comparing treatments versus the control (Statistix 7.0; Analytical Software 2000). Paired t-tests were used for the soil injection trials having only two treatments. Data are reported as untransformed means ± stan- dard error (SE). Abbott’s (1925) formula: corrected % mor- tality [(y − x)/y] × 100] where y and x are percentage survival in control and treatment, respectively, was used to adjust for control mortality in trials evaluating foliar sprays or trunk-injected systemic insecticides to control crawlers. In such cases, both actual and adjusted mortality are reported. Foliar Sprays Targeting Settled Crawlers Three trials, intended to simulate whole-canopy sprays with optimal spray coverage, evaluated control of settled crawlers on leaves. Treatments were applied to separate tagged shoots and blocked within trees. Sprays were applied to runoff using 946-mL (1-qt) handheld trigger-type sprayers (Delta Sprayer; Delta Industries, North Hollywood, CA) held approximately 15 cm (6 in) from the foliage. Each insecticide was applied at the label rate for scale insects (Table 1). The first trial was done in heavily infested sugar maples, Figure 1. Life stages of calico scale targeted in this study: (A) crawlers hatching from beneath senescing and re- cently dead adult females in mid to late May; (B) settled crawlers along veins on abaxial leaf surface; (C) over- wintering female nymph on bark showing dorsal wax plates. Acer saccharum Marshall. Treatments were applied on 23 June 2001, 33 days after first observed crawler hatch, and included bifenthrin, acephate, insecticidal soap, insecticidal oil, and water only (Table 1). Tagged shoots were collected on 11 July (18 days after treatment), and numbers of dead and total settled crawlers on all leaves were counted with a bin- ocular microscope at 25× magnification. Live settled crawlers are yellowish and turgid with angular wax plates covering the dorsum, whereas dead settled crawlers were orange to red, translucent, dehydrated, and paper-thin and sometimes miss- ing the wax plates. The rationale for counting both dead and total crawlers was to account for crawlers that might have dropped or fallen from leaves after being affected by treat- ments. The second trial, targeting settled crawlers later in the growing season, was blocked within six heavily infested hackberry trees. Sprays were applied on 20 July 2002, 55 days after first observed crawler hatch and approximately 5 days after settled crawlers began molting to second instars. Treatments were the same as previously mentioned, except that pyriproxyfen (Distance IGR) and carbaryl were added. Pyriproxyfen, a juvenile hormone analog with translaminar ©2006 International Society of Arboriculture
July 2006
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