Chroococcales

Chroococcales are an order of cyanobacteria that, under specific environmental conditions, can proliferate significantly, forming dense colonies that impact agricultural crop development. While often considered beneficial soil microorganisms, their uncontrolled growth on the surface of growing media can negatively affect the physiological health of greenhouse-grown plants.

The primary nature of this biological interference involves the formation of slimy, mucilaginous mats that coat the soil or growth substrate surface. These mats act as a physical barrier, significantly reducing gas exchange, blocking water absorption in the substrate, and interfering with the healthy transpiration and respiration processes of the host plant tissues.

Commonly affected crops include vegetable transplants, hydroponically grown greens, and ornamental plants in greenhouses. Symptoms include the emergence of a distinctive dark green or blue-green film on the soil surface, which may spread to the stems and lower leaves of seedlings, resulting in stunted growth, chlorosis, and in severe cases, plant decay.

Development and spread are primarily favored by persistent high humidity, poor soil aeration, and water stagnation. High levels of light exposure combined with stagnant water create an optimal environment for these organisms to reproduce rapidly. Greenhouse operations with inadequate drainage and insufficient ventilation are particularly susceptible to widespread outbreaks.

Management and prevention focus on creating conditions unfavorable for cyanobacterial growth. Essential practices include installing effective drainage systems, ensuring proper ventilation to reduce surface humidity, and applying copper-based algaecides or fungicides to treat the substrate. Regular surface cultivation can also disrupt colony formation and improve soil oxygen levels, effectively mitigating the threat to the crop.