Weak plants are most susceptible to Alternaria leaf spot. The fungus is spread in wind and rain and is favored by warm, wet conditions. Angular Leaf Spot Angular leaf spot, caused by the bacterium Pseudomonas lachrymans, affects cucumber, squash, and pumpkin. Leaf spots are angular in appearance, being limited by major veins. They are water soaked initially and eventually turn grayish brown.
Leaves take on a shot-holed appearance as spots drop out.
The bacterium also produces small, water-soaked spots on fruit, which can lead to rotting of the fruit. The disease is favored by warm, wet conditions. Plant certified, disease-free seed. Plant in well-prepared, fertile soil. Plant resistant varieties when available.