140 Hubbard and Potter: Managing Calico Scale Infestations Table 1. Products and rates used in field trials against E. cerasorum. Active ingredient Trade namez Foliage/bark spray formulations Acephate Bifenthrin Carbaryl Cyfluthrin Horticultural oil Insecticidal soap Pyriproxyfen Soil-injected formulation Imidacloprid Trunk-injected formulations Dicrotophos Imidacloprid Orthene TTO Talstar Lawn/Tree Flowable Sevin SL Tempo SC Ultra Superior Miscible Spray Oil Polyethylenes and polyterpenes Transfilm Merit 75 WP Inject-a-cide “B” with bidrin Imicide 75.0 7.9 43.0 1.8 Safer Yard & Garden Insect Killer 49.5 Esteem 35 WP 95.0 35.0 Not specified 75.0 82.0 10.0 AI (%) in product Field ratey 787 mg/L (10.5 oz/100 gal) 1.7 mL/L (21.7 fl oz/100 gal) 2.5 mL/L (1 qt/100 gal) 0.41 mL/L (5.4 fl oz/100 gal) 20 to 30 mL/L (2 to 3 gal/100 gal) 19.5 mL/L (1.95 gal/100 gal) 371 mg/L (5 oz/100 gal) 50 or 100 mL/L (5 or 10 gal/100 gal) 1.96 g/2.54 cm (0.07 oz/1 in) trunk diameter 2 mL/5.1 cm (0.07 fl oz/2 in) trunk diameter 4 mL/5.1 cm (0.14 fl oz/2 in) trunk diameter zProduct (sources): Orthene, Esteem, and Distance (Valent, Richardson, TX); Talstar (FMC, Philadelphia, PA); Safer soap (Safer, Bloomington, MN); Superior Oil (Universal Cooperatives, Minneapolis, MN), Tempo and Merit (Bayer, Montvale, NJ), Transfilm (PBI/Gordon, Kansas City, MO), Imicide and Inject-a-cide “B” (Mauget, Arcadia, CA). yBased on labeled rates; for sprayable formulations, values are amount of product per liter (or gallon) of spray mix. activity, is labeled for control of scale crawlers on ornamental trees. Carbaryl was included at farm managers’ request. Ef- ficacy was determined 13 days after treatment (2 August) in the same manner as previously described. A third trial evaluated pyriproxyfen (Esteem 35 WP) against younger, settled crawlers. Cyfluthrin was included as a standard. Tagged shoots were blocked within five heavily infested hackberry trees. Sprays were applied on 23 June 2003, 29 days after the first observed crawler hatch and ap- proximately 23 days before settled crawlers began molting to the second instar. Efficacy was determined on 31 July 2003 (38 days after treatment), as before. Preventive Sprays at First Crawler Hatch Controlling settled crawlers with contact insecticides requires that spray residues reach the nymphs, which nestle mainly along veins on abaxial leaf surfaces. We speculated that sprays applied at first egg hatch might be more effective than targeting settled crawlers because the active first instars would expose themselves to residues as they move from hatching sites on bark to feeding sites on leaves. That ap- proach was tested in a stand of 6 to 8 m (19.8 to 26.4 ft) tall, heavily infested sweetgum trees planted along a grassy road median. Three separate branches (each approximately 1mlong [3.3 ft]) bearing smaller twigs were blocked and tagged within six replicate trees. Tagged branches were encrusted with dozens of maturing female scales. The site was monitored daily for egg hatch, which began 20 May. That day, one tagged branch on each tree was sprayed with either bifenthrin or pyriproxy- fen (Esteem 35 WP), or was left untreated. Treatments were applied with a backpack sprayer (Solo, Newport News, VA) ©2006 International Society of Arboriculture to thoroughly wet the bark and leaves. The rest of the tree was not sprayed, ensuring ample crawlers to colonize the tagged shoots. Efficacy was evaluated 3–4 August 2004 (75 to 76 days after crawler hatch) by harvesting each treated branch, re- moving 10 representative leaves along its length, and count- ing all live settled crawlers on the left half of the abaxial leaf surface of each leaf. Leaf counts were pooled within branches and compared between treatments with trees as replicates. Targeting Postoverwintered Scales with Insecticidal Oil or Antitranspirant Horticultural oil can be effective for controlling overwinter- ing stages of certain soft scales (Johnson 1982; Baxendale and Johnson 1990). We evaluated late-winter oil sprays for control of late second instars and recently molted (not yet swollen) young adults on bark. For the first trial, lower branches (approximately 1 m long [3.3 ft]) were tagged and blocked within six heavily infested hackberry trees. Branches were sprayed to runoff with 2% or 3% insecticidal oil on 12 March 2002 or left unsprayed. Tagged branches were har- vested on 24 April (43 days after treatment), cut into 12.7 cm (5.1 in) sections, and 15 randomly selected sections from each branch were examined with a binocular microscope at 25× to determine total living and dead scales. A second trial evaluated whole-canopy application of 2% insecticidal oil. Twelve heavily infested hackberry trees (20 to 25 cm [8 to 10 in] diameter) were randomly divided into treated or con- trol groups. Treated trees were sprayed on 6 March 2002, using a hydraulic spray unit (Kappa-55; Udor, Lino Lakes, MN) and spray gun havinga7mm (0.28 in) diameter tip opening that delivered 38 L (10 gal)/min and 20.9 kg/cm2
July 2006
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