Phomopsis blight of pepper

The fungus Diaporthe capsici (anamorph Phomopsis capsici) is the causal agent of Phomopsis blight, a serious fungal disease affecting pepper crops worldwide. This pathogen is particularly destructive as it colonizes both vegetative tissues and fruits, causing significant yield losses and reducing the market quality of the harvest.

The host range is primarily focused on the Solanaceae family, with peppers being the most vulnerable. The disease can be transmitted via contaminated seeds, soil debris, and water splashes. Because the pathogen is capable of surviving in the soil for extended periods, it presents a consistent challenge for continuous cropping systems that do not employ proper rotation.

Symptoms often manifest as sunken, necrotic spots on developing fruits. As the disease progresses, these lesions enlarge and exhibit characteristic tiny black fungal structures, known as pycnidia, embedded within the dead tissue. On stems, the disease creates dark lesions that can girdle the plant, leading to wilting, stunted growth, and eventual death of the plant parts above the infection site.

Environmental conditions play a crucial role in disease development. High humidity levels, prolonged periods of leaf wetness, and moderate temperatures ranging from 20°C to 28°C provide the ideal environment for conidial production and dispersal. Poor air circulation in greenhouse environments significantly exacerbates the rapid spread of the fungus among plants.

Effective management strategies include the use of certified, disease-free seeds and the implementation of a strict 3-4 year crop rotation cycle. Sanitation is paramount; removing and burying or burning infected plant debris helps reduce the primary inoculum load. During the growing season, applying protective or systemic fungicides at the early onset of symptoms is essential to prevent large-scale epidemics.