Dry rot of sweet potato

The fungus Diaporthe batatas, historically known as Phomopsis batatas, is the primary causal agent of dry rot in sweet potatoes. This pathogen is a significant threat to post-harvest quality, often remaining dormant during growth and manifesting symptoms only after the crops are stored.

Sweet potato (Ipomoea batatas) is the main host plant for this fungus. Infection typically initiates through entry points such as wounds, cracks, or bruises caused during harvesting, handling, or by soil-dwelling pests that compromise the protective skin of the tuber.

Symptoms of dry rot include sunken, circular, dark-brown spots on the surface of the tuber. Unlike soft rots, the tissue beneath these spots remains relatively dry and leathery. Over time, the internal flesh may develop a spongy or powdery texture as the fungus consumes the starch reserves, ultimately leading to the complete decay of the storage root.

Environmental conditions play a critical role in the development and spread of Diaporthe batatas. High ambient humidity and warm temperatures inside storage facilities significantly accelerate the colonization of the fungus. Furthermore, contaminated tools and the reuse of infested soil create an environment where the disease cycle perpetuates.

Effective management requires a combination of sanitation and proper post-harvest handling. Growers should focus on careful harvesting to prevent skin damage, thorough curing of the roots at appropriate temperatures, and maintaining adequate ventilation in storage units. Rotating crops and removing infected crop debris from fields are also essential preventative practices.