Potato dry rot: What causes potato dry rot?

Horticulturists have to deal with an impressive number of absolutely repulsive plant diseases, but for the potato grower, few of them can exceed the level of thickness that develops in potato dry rot. With great care you can prevent the potato dry rot disease from spreading in your garden, but once a potato tuber is infected, treatment is not possible.

What causes potato dry rot?

Dry rot of potatoes is caused by several fungi of the genus Fusarium . Fusarium fungi are relatively weak fungi, unable to attack potatoes with intact skin, but once inside the tuber, these pathogens cause significant problems and allow other diseases, such as bacterial soft rot, to take hold. Potato dry rot is more common in the spring and fall and can remain dormant in the soil. Spring diseases can quickly kill young potato plants, but diseases contracted in the fall are much more damaging to established crops.

Symptoms of potato dry rot are difficult to detect in the aerial parts of the plant, but once the tubers are dug up, they cannot be missed. Affected tubers may be completely dry rotten, crumbling to the touch, or in various stages of decomposition. Cutting a tuber in half reveals brown to black, blue-like spots that gradually lighten at the edges and rotten cores that may contain white, pink, yellow or leafy fungal structures.

How to treat potato dry rot

Infected potatoes cannot be treated, but the spread of the disease can be prevented and the risk of transmission minimized. Since there are no truly dry, rot-free seed potatoes, efforts should focus on preventing standing water and mechanical injury to tubers. Handle potatoes with care upon receipt, waiting for seed potatoes to be cut until the tissue temperature is above 50 F. (10 C.).

Treatments against flutolanil-mancozeb or fludioxinil-mancozeb, fungi of seed potatoes, are strongly recommended before planting, as well as waiting until the soil reaches about 60 F. (16 C.). Prevention of tuber skin injury is of the utmost importance to preserve your crop; whenever you have to cut a potato, make sure to disinfect the tools before and after cutting. Remove potatoes with obvious symptoms of disease; do not plant them in the soil or compost them.

Take the same precautions with your potato stand as with seed potatoes. Brush the soil thoroughly when checking your tubers rather than planting a fork or shovel nearby. The more you reduce the risk to the potato skin, the more likely you are to get a crop free of dry rot.