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Chemical control of Cytospora leucostoma, a major limiting factor of peach production in western Colorado




Miller, Stephan, author
Stewart, Jane, advisor
Minas, Ioannis, advisor
Norton, Andrew, committee member
Uchanski, Mark, committee member

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Cytospora canker, Cytospora leucostoma, is a major limiting factor of peach production in Colorado, accounting for 15-20% of crop production loss annually. Given the unique environmental factors of the western slope region of Colorado, C. leucostoma has developed into a severe fungal disease, reducing yields annually. Chemical measures are important for Cytospora control as few options currently exist for preventing new infections. The specific objectives of the following thesis are to: (1) evaluate the efficacy of conventional and organic fungicides for C. leucostoma control, (2) test wound sealing fungicides, embedded in paint or kaolin clay, to develop preventive and containment approaches in existing orchards. Topsin, Topsin amended in 50% latex, Captan, Captan amended in 50% latex, 50% latex, lime sulfur, and lime sulfur amended in kaolin clay (Surround WP) showed evidence of efficacy from laboratory and field trials. Of these treatments, 50% latex, Topsin amended in 50% latex, and Captan amended in 50% latex, were shown to limit pathogen growth most effectively on pruning wounds during field trials in the summer season. In all field trials, however, NuCop showed absolutely no efficacy and should be avoided for C. leucostoma control in western Colorado. When various chemicals were tested on existing cankers to reduce spore inoculum loads, efficacy could not be statistically confirmed. The results of this study were compicated by variable field conditions and a large range of spore produced by each canker. Thus, larger sample sizes should be used in future studies to tease a part chemical efficacy and abiotic influences. Further, kaolin clay alone may shield fungal cankers from extreme temperatures, enhancing its growth in the field.


2017 Fall.
Includes bibliographical references.

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