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Epidemiology of Cytospora leucostoma: A Major Limiting Factor for Colorado Peach Production

Stephan Miller: Colorado State University

<div>In western Colorado, <em>Cytospora leucostoma</em> is ubiquitous in peach orchards, and has developed into a major limiting factor of peach production. The annual epidemiology patterns of <em>C. leucostoma</em>, specific to the western Colorado climatic conditions are not well known. Epidemiology studies are important for growers to develop well-rounded management strategies targeting seasons of heightened infection periods. Our specific objectives were to: a) monitor spore production and lesion size monthly for one year, b) evaluate mycelial growth when incubated in various temperatures, and c) evaluate conidial germination when exposed to different temperatures. Trends in monthly field spore production, and spore germination assays, indicate a fitness decrease when <em>C. leucostoma</em> is exposed to extreme temperatures and percent relative humidity. Despite this fitness decrease, cankers were shown to sporulate year-round in western Colorado. When colonies were incubated, mycelial growth was quickest and most abundant under 28°C and halted at 10°C and 37°C. In monitoring the epidemiology of <em>C. leucostoma</em>, management standards in western Colorado can be adjusted to decrease future infections within existing orchards thereby increasing orchard longevity.</div>