Anthracnose of cucurbits

The fungus Colletotrichum bryoniicola is the primary causal agent of anthracnose in a wide variety of cucurbitaceous crops. This pathogen is highly destructive and can significantly compromise both vegetative growth and fruit quality, often leading to total crop failure if left unmanaged in favorable environments.

This disease primarily impacts plants such as cucumbers, melons, watermelons, pumpkins, and squash. While it can occur in open field cultivation, the conditions prevalent in greenhouses — such as high humidity and restricted airflow — make these facilities particularly vulnerable to rapid spread and infection cycles throughout the growing season.

Early symptoms include the appearance of small, water-soaked, yellowish or tan spots on leaves, which eventually enlarge and become necrotic. As the disease progresses, sunken, brownish ulcers develop on stems and petioles, leading to structural weakness. Infected fruits display circular, sunken spots that often develop a pinkish mass of fungal spores under moist conditions, resulting in rapid fruit decay.

Environmental conditions are critical for the lifecycle of Colletotrichum bryoniicola. The disease thrives in high humidity and temperatures between 20°C and 28°C. Spores are dispersed through splashing water, irrigation, farm machinery, and worker contact. The fungus can persist in soil, crop debris, and contaminated seeds for several seasons, complicating control efforts in successive plantings.

Integrated pest management (IPM) is essential for controlling anthracnose. Key strategies include using certified disease-free seeds and selecting resistant or tolerant cultivars. Cultural practices such as maintaining proper plant spacing, ensuring adequate ventilation to reduce leaf wetness, and meticulous cleanup of crop residues after harvest are vital. Chemical control involving timely application of approved fungicides is also recommended when environmental conditions favor disease development.