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Evaluation of fungicides for the prevention of boxwood blight, 2012.

K. L. Ivors, L. W. Lacey, and M. Ganci

Dept. Plant Pathology, North Carolina State Univ.

455 Research Drive, Mills River, NC 28759

This trial evaluated the efficacy of several commercially available fungicides for preventive activity against boxwood blight caused by Cylindrocladium buxicola. Treatments were arranged in a randomized complete block design consisting of four replications of six 1-gal English boxwood plants per treatment on a container pad at the Mountain Horticultural Crops Research Station in Mills River, NC. Treatments were applied as foliar sprays until runoff with a CO2-pressurized backpack sprayer equipped with a handheld boom and a single, hollow-cone nozzle (TXVS-26) delivering 50-60 psi. Treatments were applied on 13 Sep, 28 Sep, and 13 Oct. Inoculum was prepared by flooding Petri-dishes of 10 day cultures of the pathogen growing on PDA. Plants were spray inoculated with 5,000 spores per ml until runoff one day post treatment on 14 Sep, and again on 30 Sep, two days after the second fungicide treatment with 8,000 spores per ml until run-off. Disease assessments were conducted on 1, 16 and 26 Oct. Percent leaf area diseased was recorded using the standard Horsfall-Barratt scale. Disease pressure was not high enough to evaluate percent leaf drop or percent stem streaking. AUDPC for percent leaf area diseased across the entire timeframe of the trial was calculated. Air temperatures during the trial was suboptimal for high rates of infection with average daily high and low temperatures of 77.7 and 55.4°F for Sept; and 66.3 and 43.5°F for Oct.

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