Nostocales cyanobacteria

The order Nostocales comprises cyanobacteria known for their nitrogen-fixing capabilities and photosynthetic activity. While they are beneficial in natural ecosystems, their uncontrolled growth in greenhouses and intensive farming systems can negatively impact crop production. They are not plant pathogens in the traditional sense, but their presence acts as an environmental stressor for cultivated plants.

These organisms primarily affect nursery seedlings, hydroponic systems, and potted plants kept in highly humid environments. By forming a dense mat over the soil surface, Nostocales can significantly reduce soil porosity. This crust creates a barrier that hinders gas exchange and water infiltration, which is particularly detrimental to young, developing root systems.

The visual signs of infestation include the appearance of a dark green, bluish, or brownish gelatinous crust on the surface of the growing medium. Once dried, this crust becomes hard and cracked. Affected crops often display symptoms of stunted growth, chlorosis, and poor root development due to the anaerobic conditions created by the algal mat surrounding the plant base.

Development is driven by excessive moisture, high light intensity, and the availability of excess nitrogen and phosphorus in the substrate. In greenhouse conditions, Nostocales thrive when irrigation water is frequently applied and drainage is inadequate. Spores can be transported through irrigation systems, contaminated tools, or air movement, quickly colonizing new areas.

Effective management focuses on creating unfavorable conditions for algal growth. Agronomic control measures include improving substrate aeration, reducing watering frequency to allow the topsoil to dry, and optimizing light exposure. Regular sanitation of pots, benches, and tools is essential to prevent re-infestation. If chemical control is necessary, copper-based algaecides or hydrogen peroxide treatments are commonly utilized.