Didymella

Didymella is a genus of fungi in the family Didymellaceae, within the order Pleosporales of the class Dothideomycetes. The genus includes numerous species that are primarily plant pathogens, causing a range of diseases on crops and ornamentals.

Taxonomy and phylogeny have shifted many species into Didymella from other genera such as Phoma and Ascochyta, based on molecular data. The sexual stage (teleomorph) of many Didymella species forms pseudothecia that produce asci and ascospores, while many species also reproduce asexually to form conidia in structures such as pycnidia. This dual reproductive pattern reflects the historical complexity of classifying Phoma- and Ascochyta-like fungi.

Ecology and disease: Didymella species have a cosmopolitan distribution and inhabit agricultural and natural ecosystems. They infect a wide range of hosts, including cucurbits (gummy stem blight), peas (ascochyta blight), beans, tomatoes, and various ornamentals. Diseases often present as leaf spots, fruit rot, stem lesions, and blights. Infections typically occur under warm, wet conditions and may persist in crop debris, allowing recurring outbreaks.

Notable species include Didymella bryoniae, the teleomorph of Phoma bryoniae, which causes gummy stem blight in cucurbits, and Didymella pinodes, the teleomorph of Ascochyta pinodes, responsible for ascochyta blight of peas. Management generally involves cultural practices such as crop rotation and sanitation, resistant varieties where available, and timely fungicide applications in affected crops.

See also: list of Didymella species.