126 Harrell: Imidacloprid Concentrations in Green Ash After Two Trunk-Injection Methods Imidacloprid Concentrations in Green Ash (Fraxinus pennsylvanica) Following Treatments with Two Trunk-Injection Methods Mark Harrell Abstract. Two imidacloprid trunk-injection products (PointerTM and Imicide) were applied to green ash (Fraxinus pennsylvanica Marsh.) in May and July to compare the concentrations of imidacloprid in sap and leaf and trunk tissues after the injections. Sap samples were extracted from shoots 0, 3, 7, 30, 60, and 90 days after treatment and analyzed for imidacloprid. Dry leaf samples were analyzed for imidacloprid at 30 and 90 days after treatment. Combined xylem and cambial zone samples were analyzed for imidacloprid at 90 days after treatment at 0.5 m (1.65 ft) and 1.0 m (3.3 ft) above the injection sites. Sap imidacloprid concentrations in trees treated in May with Pointer were significantly higher than the untreated control at 7 days after treatment (P < 0.05) but were not significantly different from the control on other days or different from Imicide on any day. Sap imidacloprid levels in trees treated in July with Pointer were significantly higher than the control at 30 days after treatment but were not significantly different from Imicide. Dry leaf imidacloprid levels in trees treated with Pointer were significantly higher than the Imicide and control treatments at 30 and 90 days after treatment. Xylem and cambial zone imidacloprid levels in trees treated with Pointer were significant higher than the Imicide and control treatments at 90 days after treatment at 1.0 m (3.3 ft) above the injection sites but were not significantly higher at 0.5 m (1.65 ft). No imidacloprid levels from Imicide were significantly different from those in the untreated control trees. Key Words. Agrilus planipennis; ash; emerald ash borer; Fraxinus pennsylvanica; Imicide; imidacloprid; injection; insecticide; PointerTM ; trunk. Trunk injections are one of the new tools available to ar- borists to control a variety of insect pests and diseases. Most injection treatments compared to other methods have the ad- vantages of using much lower volumes of material, requiring simpler equipment, and placing the chemical inside the tree, where it targets the pest or disease and is much less likely to be a problem for people, wildlife, beneficial insects, and other nontarget organisms. Imidacloprid is one trunk-injectable insecticide that has been found to be effective in controlling a number of borers and sucking insect pests of trees (Gill et al. 1999; Young 2002; McCullough et al. 2004; Doccola et al. 2005). Imida- cloprid trunk injections have been a major component of the eradication efforts for the Asian longhorned beetle in New York and Illinois, U.S. (USDA 2000) and are among the recommended treatments for the emerald ash borer in Michi- gan (Smitley 2005). One of the studies conducted to test the effectiveness of imidacloprid trunk-injection treatments against the emerald ash borer suggested that PointerTM insecticide (ArborSys- tems, Omaha, NE) was not effective in controlling this pest (McCullough et al. 2004). Another report, however, de- scribed ash in Plymouth, Michigan, recovering from the em- erald ash borer following treatments with Pointer, and sug- gested that Pointer is effective (Roberts 2004). The current ©2006 International Society of Arboriculture study was conducted to re-examine Pointer for its potential to control borers such as the emerald ash borer by comparing the concentrations of imidacloprid from Pointer in sap and tree tissues with those from Imicide (J.J. Mauget Co., Arcadia, CA), a product commonly used for borer control. MATERIALS AND METHODS Green ash (Fraxinus pennsylvanica Marsh.) trees at two sites in eastern Nebraska, were trunk injected with either Pointer (5% active ingredient [a.i.] at 1 mL/15 cm [6 in] intervals around the trunk circumference) or Imicide (10% a.i. at 3 mL/15 cm [6 in] intervals around the trunk circumference) following label instructions and using label rates. Sap and tissue samples were analyzed for imidacloprid at some or all of the intervals: 0, 3, 7, 30, 60, and 90 days after treatment using QuantiPlateTM (ELISA) kits for imidacloprid (Envi- roLogix, Portland, ME). Treatments were applied on 4 May 2004, at site 1 and on 12 July 2004, at site 2. Trees at site 1 ranged in trunk diameter from 14 to 24 cm (5.6 to 9.6 in) and were approximately 7 m (23 ft) tall. Trees at site 2 ranged in diameter from 12 to 18 cm (4.8 to 7.2 in) and had an average height of approximately 6 m (20 ft). Trees were blocked by size and location, and treatments were applied randomly to trees within blocks. Each treatment and an untreated control were replicated three
May 2006
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