Emerging Fusarium Species and Their Implications for Potato Dry Rot Management

By Hafiz Muhammad Usman Aslam|

Potato production in regions such as Colorado’s San Luis Valley plays a critical role in supplying both fresh and seed potatoes to domestic and international markets. However, storage diseases-particularly Fusarium dry rot-continue to threaten tuber quality, marketability, and overall profitability. Recent research conducted at Colorado State University’s San Luis Valley Research Center highlights an evolving challenge: the presence of multiple Fusarium species associated with potato dry rot, including species not previously reported in the United States.

Traditionally, potato dry rot has been primarily attributed to a few well-known Fusarium species, most notably Fusarium sambucinum.  New Research from Colorado State University’s San Luis Valley Research Center points to an increasingly complex threat: multiple Fusarium species contributing to potato dry rot, including some not previously reported in the U.S.

A More Complex Disease Picture

One of the most important takeaways for growers and agribusiness stakeholders is that not all Fusarium species behave the same. In controlled studies, we observed differences in growth rates and aggressiveness among species. For instance, F. sambucinum exhibited rapid growth in culture, while F. solani demonstrated higher aggressiveness in tuber assays, producing larger lesions. These biological differences suggest that disease progression, storage losses, and management responses may vary depending on the dominant species present.

This variability has important consequences for postharvest disease management. Many existing management strategies have been developed with a limited number of Fusarium species in mind. However, if multiple species are present-each with different sensitivities to fungicides or environmental conditions-then a “one-size-fits-all” approach may no longer be sufficient. This highlights the need for more targeted and informed management practices based on accurate pathogen identification.

From a crop protection standpoint, the findings also raise concerns about fungicide efficacy and resistance management. Fusarium populations have historically shown the ability to develop resistance to single-site fungicides, such as benzimidazoles. The presence of multiple species could further complicate control efforts if these species differ in their sensitivity profiles. As a result, integrating fungicide stewardship with broader cultural and handling practices becomes even more critical.

Practical Steps for Growers

  1. Start with clean seed: Using high-quality seed tubers with minimal pre-existing infections can significantly reduce disease incidence later in the season. It is particularly beneficial to assess seed health during the later months of storage when symptoms are more likely to be visible.
  2. Minimize wounding: Wounds created during seed cutting provide entry points for Fusarium Ensuring that cutting equipment is clean, sharp, and regularly disinfected can help limit pathogen spread. Additionally, allowing cut seed pieces to heal under appropriate conditions before planting can reduce infection risk.
  3. Manage temperature: Warming seed tubers to approximately 50°F before cutting can improve wound healing and reduce susceptibility. Similarly, during harvest, minimizing bruising and mechanical damage is critical, as injuries significantly increase the likelihood of infection.
  4. Optimize storage conditions: Applying effective fungicide treatments with thorough coverage of tuber surfaces can help suppress pathogen development during storage. Equally important is maintaining optimal storage conditions, including proper temperature, humidity, and ventilation, to limit disease progression.
  5. Invest in Monitoring and Diagnostics: Advances in molecular tools, such as PCR and qPCR-based assays, now allow for more precise identification of Fusarium species in both field and storage environments. Incorporating these tools into routine diagnostics can enable more informed decision-making and tailored management strategies.

Looking Ahead

The discovery of diverse Fusarium species associated with potato dry rot-including newly reported species-signals a shift in our understanding of this important storage disease. For the potato industry, this means adapting management approaches to account for pathogen diversity, investing in accurate diagnostics, and reinforcing best practices in seed handling and storage. By doing so, growers and agribusinesses can better safeguard tuber quality, reduce losses, and sustain productivity in an increasingly complex disease landscape.

Acknowledgment

This research was conducted under the supervision of Dr. Mohamad Chikh-Ali, Associate Professor and Plant Pathology Program Leader at the San Luis Valley Research Center, Colorado State University, with laboratory assistance from Jeremy Daniel.

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Dr. Hafiz Muhammad Usman Aslam is presently serving as a Postdoctoral Fellow at the San Luis Valley Research Center, Colorado State University, where my research is focused on cutting-edge molecular diagnostics of plant pathogens, with a primary emphasis on potatoes and other important crops. My expertise encompasses the identification and intricate analysis of key pathogens afflicting potatoes, including Fusarium, Pythium, Phytophthora, Alternaria, Colletotrichum, Verticillium, and Pectobacterium spp. See all author stories here.

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