Stigonema

Stigonema is a genus of filamentous cyanobacteria (blue-green algae) that, under specific environmental conditions, acts as a pathogenic agent for various agricultural crops. Unlike fungal pathogens, these photosynthetic microorganisms establish dense colonial films on plant tissues, effectively acting as an epiphytic threat to plant health.

The disease frequently occurs in environments characterized by constant moisture, such as rice paddies, greenhouses, and hydroponic setups. Plants suffering from poor drainage or lack of air circulation in the root zone are highly susceptible to the rapid colonization by these cyanobacteria, which can thrive even in low-nutrient conditions.

The primary symptom of infection is the emergence of dark green to black, velvety growths on stems, leaves, and roots. These biological films create a physical barrier that restricts gas exchange and disrupts the plant's photosynthetic capacity, ultimately leading to stunted development, chlorosis, and gradual tissue necrosis if left untreated.

The development and proliferation of Stigonema are driven by excessive irrigation, high humidity, and poor ventilation. In greenhouse environments, the combination of light and moisture allows these organisms to spread efficiently via irrigation runoff, splashing water, or contact with contaminated agricultural tools.

The economic damage caused by Stigonema results from reduced vigor and secondary health issues in crops. Mitigation strategies focus on environmental management and sanitation:

• Optimization of soil drainage and greenhouse ventilation to reduce overall humidity levels.
• Implementation of precise irrigation techniques to prevent waterlogging on soil or substrate surfaces.
• Application of approved algicides and disinfectants to sanitize growing areas.
• Strict adherence to sanitation protocols to prevent the transport of cyanobacteria on tools.