Botrytis blight or grey mold (tan spot) is a common disease in Michigan potato fields. The disease is often observed on stems and leaves but when inoculum levels are high, the disease can also be seen on tubers. The lesions on foliage are very similar to and can be confused with those caused by early blight (Alternaria solani) and late blight (Phytophthora infestans). The pathogen is able to overwinter in the soil as sclerotia. Leaf and stem lesions lead to early plant death (Figure 1) and decreased yield and tuber quality. Excessive fertilizer inputs and irrigation or precipitation may lead to a dense canopy with reduced air circulation, which can remain wet for extended periods and promote grey mold. The pathogen has a wide host range with reported incidence in more than 200 different hosts, some of which are used in rotation with potatoes. This wide host range causes a drastic increase in inoculum levels over time.