POTATO CULL PILES POSE SERIOUS LATE BLIGHT RISK: RECOMMEND PROPER DISPOSAL

Potatoes that fail to meet grade standards, whether due to size, shape, damage, or other defects—are commonly referred to as culls. Cull potatoes are removed/discarded from the market stream because they do not meet quality specifications or are damaged during harvest or storage. Rather than being sold, they are typically set aside in piles until growers decide how to dispose of them. While cull piles may seem harmless, they can pose a significant threat to surrounding potato fields if not managed correctly.

Late Blight Risk Growing in Cull Piles

Among the various issues associated with cull piles, the most serious is the risk of late blight, a devastating disease caused by the fungus-like organism Phytophthora infestans. Cull piles can remain warm enough through winter to allow infected tubers and sprouting volunteer plants to survive. This creates an ideal environment for the pathogen to overwinter and multiply.

By early spring, disease can rapidly develop on the new growth emerging from these piles. Even a single unmanaged cull pile can become a starting point for a widespread, regional late blight outbreak. The threat is even greater when culls come directly from storage in late winter or early spring, as these tubers have been shielded from freezing temperatures that normally help kill infected material. Once late blight becomes active in a cull pile, spores can easily spread to nearby volunteer potatoes and newly emerging commercial crops, putting entire production areas at risk.

Recommended Disposal Practices

To minimize disease pressure and protect the region’s potato acreage, experts strongly encourage growers to dispose of cull potatoes safely and promptly. Effective options include:

• Composting – High temperatures achieved in managed compost systems help kill pathogens.
• Feeding to Cattle – When appropriate and safe, culls can be used as livestock feed, reducing waste.
• Deep Burying – Covering culls with enough soil prevents sprouting and eliminates volunteer growth.
• Other Approved Methods – Any approach that ensures tubers cannot sprout or survive the winter contributes to disease prevention.

Proper cull management is essential for safeguarding the industry. With late blight capable of spreading rapidly and causing severe economic losses, disposing of culls responsibly remains one of the simplest and most effective steps growers can take to protect their crops and the broader potato-growing community.