Characiopsis

Characiopsis is a genus of yellow-green algae that can function as a significant nuisance in greenhouse environments. While not a typical fungal pathogen, its proliferation on substrate surfaces creates unfavorable conditions for plant health, often leading to physiological stress and reduced vigor in commercial crop production.

These algae primarily affect seedling trays and potted plants in indoor cultivation systems. The organism thrives in moist environments, forming a physical barrier on the surface of the soil or growing media. This barrier interferes with the critical gas exchange between the roots and the atmosphere, which is essential for seedling development.

The characteristic symptoms of a Characiopsis outbreak include the formation of a slimy, olive-green or dark green crust on the substrate surface. Affected plants may show stunted growth, chlorosis, and in severe cases, necrosis of the seedling base. Growers often notice that water does not penetrate the substrate effectively due to the density of the algal mat.

The development of this organism is triggered by high humidity, excessive irrigation, and high levels of nutrients available on the surface of the growing medium. High light intensity in greenhouses further exacerbates the problem, providing the energy required for the algae to colonize large areas of the nursery in a very short timeframe.

Effective management strategies focus on modifying the environment to inhibit algal growth.

• Adjust irrigation schedules to allow the surface of the substrate to dry out.
• Improve air circulation to reduce relative humidity.
• Use sterilized or high-quality potting mixes.
• Maintain proper equipment sanitation to prevent spore transfer.