Synechococcales

Synechococcales are a group of cyanobacteria often encountered in agricultural settings, particularly within controlled environment agriculture (CEA) and hydroponic systems. While not traditional plant pathogens, their ability to form dense biofilms on inert substrates and irrigation equipment causes significant operational challenges and can negatively affect crop health.

These organisms predominantly affect crops grown in soilless culture, such as lettuce, tomatoes, and cucumbers. Their presence is most common in nursery environments where high humidity and light intensity overlap. They compete for nutrients and space, often clogging irrigation emitters and coating the roots, which hinders nutrient uptake and oxygen diffusion.

Symptoms of an infestation include the visible appearance of slimy green or blue-green algae mats on top of growth media like rockwool or perlite. In hydroponic setups, the nutrient solution may turn greenish and develop a distinct odor. Affected plants often show signs of stunted growth, leaf chlorosis, and restricted root development due to the lack of oxygen.

The development of these cyanobacteria is triggered by exposure to light, adequate moisture, and the availability of nitrogen and phosphorus. Greenhouse environments provide the perfect conditions for their rapid proliferation. Any stagnation of water or improper maintenance of nutrient management systems significantly increases the risk of an outbreak.

• Implement blackout covers for all nutrient reservoirs and growth media.
• Regular disinfection of irrigation pipes and hydroponic channels.
• Control light exposure to surfaces where algae might colonize.
• Use UV-sterilization or ozone treatment for nutrient solutions.
• Ensure proper airflow to keep the surface of the substrate dry where possible.

Effective management focuses on creating an environment that is unfavorable for algal photosynthesis and growth. Physical barriers, such as opaque materials, are the most effective way to prevent the formation of biofilms. Once established, chemical control via algaecides or hydrogen peroxide should be performed with caution to ensure the safety of the primary crop and the biological equilibrium of the system.