Nostoc commune

Nostoc commune is a widespread colonial cyanobacterium that frequently forms gelatinous mats on moist soil surfaces. In professional agronomy and greenhouse operations, its presence is often treated as a major environmental challenge that negatively impacts seedling emergence and general crop development.

The primary concern regarding Nostoc is its ability to create a thick, impermeable barrier over the soil surface. This layer effectively chokes the soil, reducing oxygen exchange with the roots and preventing young shoots from penetrating the surface, often leading to damping-off symptoms or stunted plant growth.

The main symptoms of colonization include the appearance of jelly-like, olive-green or dark-brown clusters that solidify into brittle flakes when dry. These colonies thrive in areas with high moisture content and constant surface dampness, frequently occurring in greenhouse flats, nursery beds, and areas with poor drainage.

The development of these cyanobacterial colonies is driven by poor environmental management. Key factors include excessive frequency of overhead irrigation, high humidity, lack of air circulation, and light conditions that favor photosynthesis in the topsoil. Once established, they can persist for long periods due to their high resilience to desiccation.

To control and prevent the spread of Nostoc, growers should implement the following agricultural practices:

• Improve soil drainage and reduce the frequency of surface irrigation to allow the top layer of soil to dry out between waterings.
• Increase air movement and ventilation within the greenhouse to lower humidity levels.
• Implement mechanical cultivation or raking of the soil surface to disrupt colony formation.
• Utilize sterile or well-draining growing media to minimize the risk of initial infestation.
• Ensure adequate lighting to promote vigorous plant growth, which helps shade the soil and discourage algal development.