Diaporthe stem canker

Diaporthe sterilis is a fungal pathogen recognized as a causative agent of sunflower stem canker, also known as Phomopsis disease. This pathogen infects the host through the leaves, moving into the stems and interfering with vascular transport, which severely limits plant development and reduces seed yield and oil content.

The primary host for this fungus is the cultivated sunflower (Helianthus annuus). The disease affects plants throughout the growing season, but the most significant economic impact occurs when infection levels are high during the vegetative growth and flowering stages, leading to premature plant death.

Symptoms initially appear as V-shaped chlorotic lesions on the leaves, which then progress toward the stem. A characteristic dark brown or black canker develops at the node where the infected leaf meets the stem. As the disease advances, the stem tissue decays, leading to lodging, which often causes major harvest losses in commercial fields.

The development of the disease is strictly dependent on environmental conditions, particularly persistent high humidity and moderate temperatures. Rain-splashed spores serve as the primary inoculum, spreading from crop debris to healthy plant tissues. The ability of the pathogen to survive in soil for several years makes it a persistent threat.

Integrated management is essential for successful control. This includes crop rotation with non-host species, such as cereals, to reduce primary inoculum levels. Furthermore, selecting genetically resistant hybrids, managing plant density to improve air circulation, and timely application of foliar fungicides during the bud development stage are standard practices for managing this disease.