cytospora canker

And since the Cytospora pathogen is not limited to peach trees, Stewart’s team will look at species diversity of the fungus across peach, apple and cherry hosts and study population genomics of the fungus as it moves around and between orchards. In the long term, this research will lead to management strategies for the Cytospora canker built on an understanding of the biology and epidemiology of the various species of the fungus.

NIFA is also supporting research by Stewart and colleague Dana Hoag of the Department of Agricultural and Resource Economics to provide new insights into the economic feasibility of various management practices. The work will illuminate tradeoffs of different choices like spraying trees with pesticides versus planting new ones.

‚ÄúWe are looking at combatting this disease from a molecular standpoint, as well as from cultural practices of growers,‚ÄĚ Stewart said.

Long battle

graduate student stephan miller
Stephan Miller with a peach tree being studied for Cytospora infection.

The work being undertaken builds on a long history of fighting the Cytospora pathogen in Colorado for Stewart, in collaboration with researchers at the Western Colorado Research Center in Grand Junction, in the heart of peach country. While Cytospora has created problems for peach growers since the 1950s, it has exacerbated over time and is now halving the lives of peach trees, which used to be in the ground for 40 years but now average around 20, Stewart said.

Several years ago, Stewart and colleagues collected isolates from different orchards and found that Colorado peach orchards are impacted primarily by only one species of the fungus, Cytospora plurivora, while in other areas of the country, the species prevalence is more diverse.

Stewart and graduate student Stephan Miller then developed a chemical treatment plan for farmers and fact sheets about the pathogen, in an effort to keep infections from killing trees before cankers take hold.

With the new funding, Stewart and graduate student Sean Wright are extending that work by combining expertise in fungal biology and population genomics with observations of farmers’ habits for managing the disease, and how those habits could be changed for the better in areas like watering techniques, chemical treatments and mulching.

‚ÄĒ Anne Manning, Colorado State University

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