Internal heat necrosis (IHN) is a nonpathogenic physiological disorder of potato tubers. It was originally described in the early 1900s and has also been called internal brown spot, physiological internal necrosis, internal browning, internal brown fleck, and chocolate spot. Potatoes with IHN have light-brown to reddish-brown necrotic patches in the parenchyma (flesh) of the tuber. There are no aboveground symptoms and no external symptoms on the tubers. IHN is generally a significant problem in the mid-Atlantic and southeastern United States, but it can also a problem in other regions of the country when high temperatures and drought prevail. This talk will cover various aspects of IHN, including symptoms and control, risk factors for developing IHN, models to predict the occurrence of IHN, varietal resistance to IHN, and current research efforts to develop IHN-resistant potato varieties.
