Cyanobacteria

Cyanobacteria, commonly referred to as blue-green algae, are prokaryotic organisms that can act as a significant stress factor in agricultural settings. While they exist naturally in many soil ecosystems, their uncontrolled proliferation under greenhouse conditions can negatively impact plant development and overall soil health.

The cultures most frequently affected by these organisms include nursery seedlings, hydroponically grown vegetables, and crops grown in high-humidity indoor environments. The presence of cyanobacteria on the substrate surface creates a physical barrier that restricts essential oxygen exchange, leading to root suffocation.

Symptoms of infestation are easily identifiable: a slimy, dark green to bluish-black crust forms on the surface of the soil or growing media. As the surface dries, this layer hardens into a dense crust, which can impede seedling emergence and cause significant mechanical stress to the stems of young plants.

The development of cyanobacteria is driven by high surface moisture, high light intensity, and the presence of residual fertilizers, particularly phosphates, in the irrigation system. These conditions allow for rapid colonization of the soil surface, especially in systems where the soil remains consistently damp.

Effective management requires a combination of cultural and physical practices. Essential measures include optimizing irrigation schedules to allow the soil surface to dry out, regular cultivation of the topsoil to disrupt crust formation, improving greenhouse ventilation, and utilizing mulch or inert top layers to block the light required for photosynthesis by these organisms.