Four fungal species behind potato dry rot identified in Colorado's San Luis Valley

For potato growers, dry rot is a quiet thief. The disease does not destroy crops in the field with dramatic wilting or visible blight. Instead, it waits - attacking tubers during storage and postharvest handling, turning sound potatoes into shrunken, corky losses that eat into a farmer's bottom line after the harvest is already in.

In Colorado's San Luis Valley, one of the top potato-producing regions in the United States, plant pathologists at Colorado State University have now identified exactly which fungal species are responsible. Their findings, published in Plant Disease, reveal four Fusarium species associated with dry rot in the valley - including one that had never been previously reported in the U.S.

Why species-level identification matters

Not all Fusarium species behave the same way. They vary in aggressiveness, how they spread, and how they respond to management practices like fungicides and storage conditions. Treating dry rot as a single, undifferentiated disease misses these critical differences.

Lead author Hafiz M. Usman Aslam, who completed the research as a postdoctoral fellow under Associate Professor Mohamad Chikh-Ali, used both structural and molecular analysis to distinguish the four species. That level of specificity has direct practical applications: it can improve disease diagnosis, guide cultivar selection and breeding for resistance, and support development of management strategies tailored to the specific pathogens present in a given region.

The discovery of a Fusarium species not previously documented in the U.S. is particularly notable. It raises questions about whether the pathogen is newly arrived or simply had not been identified before - and whether it is present in other potato-growing regions as well.

Practical stakes for growers and storage managers

Potato dry rot is not just an academic concern. The San Luis Valley produces hundreds of millions of pounds of potatoes annually, and storage losses from Fusarium infection can be economically significant. Knowing which species are present allows growers and storage managers to make more informed decisions about temperature management, chemical treatments, and variety selection.

The study's limitation is geographic scope - it focuses specifically on the San Luis Valley, and the Fusarium species composition in other major potato regions may differ. But it provides a methodological template that other regions can apply to their own pathogen populations.