Ascochyta Ray Blight -- Didymella ligulicola
Symptoms: Ascochyta ray blight causes unopened buds to rot and turn dark brown to black in color. Flower-head infection is typically one-sided if it occurs during the early stages of blossom development, and the affected petals are bound together and do not break apart easily. During the early stages of petal infection, the tissue becomes pink in color and then turns tan or brown. Leaf infection results in black, irregularly shaped lesions, while stem infection causes black lesions approximately 2.5 cm or more in length.
Conditions Favoring Disease: This disease is favored by moist conditions and temperatures between 70° and 80°F.
How Pathogen Survives/Disperses: Perithecia produce ascospores which help establish new disease foci and spread inoculum to the top floral tissues of the plant. Pycnidia produce conidia that help enlarge established foci when dispersed by water splash.
Photo and write up provided by Syngenta Professional Products