Causal Agent: (fungus ‑ Alternaria cucumerina)
Lesions are round to irregular target spots on older leaves (Image 1). The symptoms are first observed at the crown of the plant. As the spots enlarge, concentric rings are formed in the lesion. The disease is favored by continuous wet conditions. The fungus is controlled with a 2 year cucurbit-free rotation, destruction of the previous crop residue and application of fungicides as needed. At the end of the growing season, plow under crop residue.