142 Hartman et al.: Therapeutic Treatments to Manage Oak Bacterial Leaf Scorch Knife, Inc, Allison Park, PA, U.S.). Drilled holes, spaced about 15 cm apart on the root flares, were fitted with a series of plas- tic “tees” and harnessed to the output of a hand pump sprayer to deliver the required suspension evenly all around the tree. Micro-injections were done with a microinjection device (M3 Microinjector, Rainbow Treecare Scientific Advancements, Minnetonka, MN, U.S.), which was capable of generating pres- sure to facilitate uptake of the solution being applied. Appli- cations were made through 0.4 cm diameter holes drilled into major root flares at the base of the tree and spaced 15–20 cm apart around the tree. Basal trunk soil drench applications and trunk spray applications were applied as previously described. Experiment 2 Table 1. Pin oak (Quercus palustris) trunk and basal drench treatments (Summer 2005). Treatments (1) Untreated Control (2) surfacantz (3) surfacantz (applied twice) (4) surfacantz (5) surfacantz (6) surfacantz sulfatev (7) surfacantz sulfatev (8) PBZw + streptomycin (applied twice) (basal drench) zPentrabarkTM yMyco-Shield® , Agrichem, Medina, OH, U.S. , Nufarm, Burr Ridge, IL, U.S. xAgrifos, Agrichem Manufacturing Industries Pty. Ltd., Loganhome, Queensland, Australia wCambistat, Rainbow Treecare Scientific Advancements, Minneapolis, MN, U.S. vAgrimycin 22.7%, Nufarm, Burr Ridge, IL, U.S. 5.9 g/L 1.6 g a.i./cm DBH - + phosphitex + PBZw + streptomycin 25% solution by volume 33% solution by volume 5.9 g/L + oxytetracycliney + oxytetracycliney Product Rate - 5.9 g/L 5.9 g/L Surfactant Rate - 2.5% by volume 2.5% by volume 2.5% by volume 2.5% by volume 2.5% by volume 2.5% by volume To determine the best application timing in spring, additional plots were established at Stone Street Farm in 2007. Fifty pin oak trees with an average DBH of 55 cm were selected for this experiment. Oxytetracycline hydrochloride was injected during spring 2007, into trees using the micro-injection technique, but with 0.6 cm diameter drill holes. The first group of oaks was in- jected on May 8–9, a second group approximately three weeks later on May 29–30 or June 1, and a third group on June 18 or 20. The first group received injections when first new leaves were fully expanded. Compared to normal seasonal leaf phenology, the timing was delayed a week or two because of an early April 2007 freeze. Chemical uptake time using this sys- tem ranged from 10 to 30 minutes. Calcium com- plex oxytetracycline was applied similarly but with an approximately two-day uptake time due to the more viscous formulation used. Treatments are listed in Table 3. Based on data from the previous year (2006), average leaf scorch was 40%–50% for each treatment group. The five treatments were replicated 10 times and the experiment was estab- lished in a randomized complete block design. Be- ginning with first symptom appearance, trees were evaluated for percent scorch symptoms at roughly two-week intervals, on August 7 and 20; Septem- ber 4 and 18; and October 2, 16, and 30, 2007. Experiment 3 To test the efficacy of root flare injection of anti- biotic on pin oaks growing as street-side trees, plots were established in a Lexington neighbor- hood with a history of bacterial leaf scorch dis- Table 2. Root flare injection, basal drench, and trunk treatments (Summer 2006). Treatment Date (1) Oxytetracycline hydrochloridez (2) Oxytetracycline hydrochloridez (3) Oxytetracycline hydrochloridez + PBZy June 21 or June 22 June 26 or June 27 June 21 or June 22 + June 1 or June 2 Rate 0.6 grams in 150 ml water per 2.5 cm tree diameter 0.6 grams in 9 ml water per 2.5 cm tree diameter 0.6 grams in 150 ml water per 2.5 cm tree diameter + 4 grams a.i. per 2.5 cm tree diameter (rate F from Cambistat application rate card) (4) Oxytetracycline hydrochloridez + PBZy June 26 or June 27 + June 1 or June 2 0.6 grams in 9 ml water per 2.5 cm tree diameter + 4 grams a.i. per 2.5 cm tree diameter (rate F from Cambistat application rate card) (5) PBZy (6) Surfactant + phosphitex (7) Oxytetracycline phosphatew (8) Untreated control June 1 or 2 June 5 June 29 - 4 g a.i. per 2.5 cm DBH 2.5% solution + 25% solution in 1.5 liters 0.6 grams in 9 ml water/ 2.5 cm tree diameter - zBacastat OSC, Rainbow Treecare Scientific Advancements, Minneapolis, MN, U.S. yCambistat, Rainbow Treecare Scientific Advancements, Minneapolis, MN, U.S. xAgrifos, Agrichem Manufacturing Industries Pty. Ltd., Loganhome, Queensland, Australia wBacastat OSP, Rainbow Treecare Scientific Advancements, Minneapolis, MN, U.S. ©2010 International Society of Arboriculture pressurized microinjection - basal drench trunk spray from the ground to 2 m pressurized microinjection + basal drench Application method pressurized macroinjection pressurized microinjection pressurized macroinjection + basal drench
May 2010
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