Gummy stem blight

Stagonosporopsis citrulli is a pathogenic fungus that causes a severe disease known as Gummy stem blight. This pathogen affects a wide range of cucurbitaceous crops, including cucumbers, watermelons, melons, and squash, posing a significant threat to global greenhouse and field vegetable production.

The fungus is characterized by its ability to infect all stages of plant development, from seedlings to mature vines and fruits. It is particularly destructive during periods of high humidity, causing lesions on stems, leaves, and fruits that significantly reduce both the quality and the total yield of the harvest.

Initial symptoms often appear as small, water-soaked spots on leaves that eventually enlarge and turn brown or black. On the stems, the infection manifests as elongated cankers, which often exude a gummy, amber-colored sap—a classic hallmark of the disease that gave it its common name. Severe stem lesions can lead to rapid wilting and plant death.

Environmental conditions play a crucial role in disease epidemiology. The fungus thrives in temperatures between 20°C and 25°C and requires prolonged periods of leaf wetness or high relative humidity to sporulate and infect healthy tissue. Because the pathogen can persist on seed coats and in contaminated plant debris, it is difficult to eradicate once it establishes in a field or greenhouse.

Effective management requires an integrated approach. Growers should prioritize the use of disease-free, certified seeds and resistant cultivars. Cultural practices such as maintaining low humidity in greenhouses, removing crop residues after harvest, and implementing a strict rotation schedule are essential. Chemical control, including the application of systemic and contact fungicides, remains necessary under high-pressure conditions.