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Annual Report: 2006
Biological Control of Sclerotinia sclerotiorum
Research was conducted to evaluate the ability of Contans (commercial bio-based product containing Coniothyrium minitans) to reduce sclerotial populations of Sclerotinia sclerotiorum in fields in New York. The objectives were 1) to quantify decline in populations of sclerotia of S. sclerotiorum following a single application of Contans (C. minitans), and 2) to determine if applications of Contans results in a reduction in plant disease caused by S. sclerotiorum. Using a wet sieving technique to recover sclerotia in soil, baseline levels of soil populations of sclerotia were determined in several naturally infested commercial fields in various cropping systems. In addition, one field at the New York State Agricultural Experiment Station in Geneva was artificially infested with sclerotia of S. sclerotiorum. The numbers of sclerotia detected in the unamended soil varied from 0 to 30 per liter of soil. The highest naturally infested field averaged 7.3 sclerotia per liter. This is equivalent to 2.95 x 106 sclerotia per acre to a 4-inch soil depth. Sclerotial populations were reassessed following the application of Contans at 1 to 4 months and in subsequent years in some fields. Populations rapidly declined to below detection levels with or without application of Contans, but in some fields, the decline was faster following application of Contans. Aggregated distribution of sclerotia in the field made enumeration problematic, but even low levels of sclerotia in the soil represent potentially many infective ascospores. Contans did not decrease sclerotial populations beyond the year of application in these trials, indicating that Contans must be reapplied when susceptible crops are planted. In our trials, disease incidence in subsequent crops following application of Contans was variable. Improved product use recommendations were generated by integrating our research results with information from product representatives and producers.
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