Eliminate Potato Cull Piles Before Crop Emergence

Late blight is one of the most devastating fungal diseases of potatoes. Once the disease develops in potato fields, it cannot be eradicated; fungicides will only slow the spread of the disease. Thus, the best defense is to keep late blight out of the field.

Cull piles can be sources of late blight spores all season long. The fungus may produce spores on the surface of infected tubers even before there are sprouts. The spores can be spread very quickly and very far by wind.

Cull potatoes accumulate whenever potatoes are graded: when harvesting, when moving tubers into or out of storage or when cutting seed for planting. A cull potato can be a whole tuber, a seed piece or even the slivers left after cutting seed. Any piece with an eye may produce a sprout and a new plant.

There are several ways to eliminate cull piles in the spring before crop emergence:

• Feed the potatoes to livestock
  
• Cover the pile: This method can be used only with small cull piles. Distribute the tubers evenly then cover them with black polyethylene plastic. The tubers will heat up and break down eventually. Sawdust or another absorbent material can be used to soak up the potato runoff and then removed from the site.
  
• Bury the cull pile: Cover cull piles with at least 4 feet of soil. Monitor the site at least twice a week during the summer If any plants emerge, pull them out or spray the shoots with a herbicide. Add extra soil if the cull pile settles during decomposition.

Destroying cull piles in the spring is an important prevention practice that should reduce the risk of late blight in your fields.

Potato plant emerging from a cull pile

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