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POSTERS: Cultural control

The effects of sanitizers on Calonectria pseudonaviculata and C. henricotiae conidia and microsclerotia viability.
Nina Shishkoff - USDA ARS FDWSRU. Richard Cowles- The Connecticut Agricultural Experiment Station, James LaMondia- Connecticut Agric Exp Station

The boxwood blight pathogens Calonectria pseudonaviculata (Cps), and C. henricotiae (Che), produce microsclerotia (ms) on and in leaf tissue and conidia in sticky masses that can be spread. We evaluated the effects of sanitizers on conidia, excised ms or all Cps life stages in 4-mm-d leaf disks. Leaf disks and excised ms were exposed to sanitizers or water for 3 to 180 min (disks), or 0.5 to 30 min (ms), wicked dry and placed onto ˝ PDA to determine viability. Conidia were loaded onto a filter, exposed to alcohol concentrations for between 2 s to 2 min and rinsed with water. Filters were backwashed with air to transfer conidia onto water agar and the percent germination was counted after 24 h. Cps in leaf disks was killed within 10-12 min for 70% ethanol and between 2-3 h for 0.525% NaOCl. Chlorophenol did not eliminate Cps from tissue. Individual ms were killed by 70% ethanol in 4 min. In contrast, ms exposed to 0.525% NaOCl or 0.05% chlorophenol for 30 min retained viability. Exposing conidia of Cps and Che to 10%, 25%, 40% and 70% ethanol demonstrated no germination after 20 s in 25% ethanol or 5 s for 40 and 70% ethanol. Conidia of Cps and Che exposed to 70% isopropanol were also dead within 5 s. A dose-response study for ethanol and isopropanol estimated 99% mortality from exposure to 63.6% alcohol for 2 s, with no difference between the alcohols. Ethanol and isopropanol can be used to quickly and inexpensively disinfest tools and contaminated surfaces.