Warm and wet weather favor the occurrence and spread of Cercospora leaf spot. The disease is primarily limited as leaf spots on foliage and rarely on petiole and stem.
Cercospora leaf spot is initially seen as small circular, yellow spots on older leaves. The size and the number of spots can increase severely at later stages of the disease.
The yellow spots turn necrotic and when lesions expand it may remain circular or can be seen as irregular shaped lesion. These symptoms can be confused with early symptoms of other diseases.
Large black margins can be seen around the lesions with a marginal yellow halo. The disease can be easily spread inside the canopy under the right environmental conditions.
The center of the lesions dry out and has a white appearance. The lesions may coalesce to form blighted areas on the leaves. Systemic yellowing may follow.
Severely affected plants have numerous leaf spots inside the canopy, plants turn severely yellow and fruits will be exposed to injury from sunscalding.
Cercospora spp. conidiophores and conidia (spores). The spores an easily move through wind and in free moisture. The pathogen can survive on crop debris, volunteer plants and cucurbit weeds.