Cull potatoes must be kept non-viable on a daily basis after May 15 in Idaho’s upper Snake River valley east of Raft River. Even though April 15, the date for the same requirement west of Raft River has passed, there are reports of viable cull piles in the Magic and Treasure Valleys. Check for the cull management regulations and dates in your area.
Cull potatoes are those that are not acceptable for use due to failure to meet size, grade, or quality standards, or due to over-supply. These “waste” potatoes are deposited in what are commonly described as cull piles that if left untended can become sources of disease, insect pest, and nuisance problems. For example, cull potatoes can harbor the pathogen that causes late blight, and University of Idaho research shows they are a reservoir for Potato virus Y and other potato viruses.
Cull piles can attract crop pests such as aphids which transmit viruses that infect potato and Colorado potato beetle. NOTE: Even if culls are not sprouting in the pile, the late blight pathogen can sporulate on infected tubers. Decomposing cull piles can also lead to public nuisance issues such as flies, odor, and leaching of excess nutrients into ground and surface waters. In addition, soil associated with cull potatoes can be infested with pests such as the powdery scab pathogen, nematodes, and weed seeds.
For these reasons, the Idaho State Department of Agriculture requires cull potatoes from all potato operations to be rendered non-viable on a daily basis after April 15th in western Idaho and after May 15th in eastern Idaho as previously mentioned. This regulation continues through September 20th and is in place to help eliminate a potential source of problems for the current season crop and to aid in maintaining the overall integrity of Idaho’s potato crop production and quality. Cull disposal must be accomplished in an environmentally safe, legal, and effective way. Monitor culls diligently. Don’t assume that freezing temperatures or prior management practices have killed the culls.
Options for destroying cull potatoes include:
- Winter field spreading
- Livestock feed
- Plastic covers
- Chemical applications
More information on the first four options can be found at http://www.cals.uidaho.edu/edComm/pdf/CIS/CIS0814.pdf (Cull and Waste Potato Management, CIS 814).