Cyanobacterial crust

Cyanobacterial crust (Cyanobacteriaceae) is a biological phenomenon where mass proliferation of cyanobacteria creates a restrictive layer on the soil surface and plant tissues. Although these organisms are naturally occurring, their overgrowth in agricultural environments acts as an opportunistic disease, negatively affecting plant development and nutrient uptake.

The causal agents belong to the family Cyanobacteriaceae, representing prokaryotic photosynthetic organisms. They are not classic pathogens, but they behave as suppressors when they develop into thick, mucilaginous mats. The damage occurs due to physical blockage of the soil surface and competition for light and space during the early developmental stages of plants.

This condition primarily affects crops in protected environments, including greenhouse vegetables like tomatoes, cucumbers, and ornamental seedlings. It is particularly common in systems utilizing hydroponics or wet soils with high nitrogen content, which encourages rapid algal colonization of the growth medium.

Key symptoms include the appearance of dark blue-green or black slippery mats on the soil or substrate surface. As the crust dries, it hardens and cracks, which causes physical damage to tender root systems and plant stems. This physical barrier prevents proper gas exchange, leading to stunted growth, wilting, and increased susceptibility to secondary fungal infections.

Control and prevention strategies focus on altering the environmental conditions that favor cyanobacteria. This includes implementing better drainage, reducing excessive irrigation, and ensuring proper air circulation in greenhouses. Chemical control using copper-based algaecides or specialized soil disinfectants may be necessary in severe outbreaks to effectively eliminate the crust.