Yellow-green algae

Yellow-green algae (Xanthophyceae) represent a class of microscopic organisms that can act as opportunistic colonizers in agricultural settings. While primarily aquatic or soil-based, under specific favorable conditions, these organisms bloom on the surface of cultivation media, negatively impacting crop development and soil structure.

These organisms are most frequently observed in greenhouse environments, nurseries, and poorly drained fields. They target young seedlings, vegetable crops, and ornamental plants, specifically in systems utilizing frequent irrigation or constant moist surfaces, such as hydroponics or high-humidity propagation benches.

Symptoms are identified by the development of a distinct yellow-green or brownish gelatinous crust on the soil surface. As the surface dries, this crust hardens, creating a physical barrier that prevents gas exchange, restricts root oxygenation, and physically hinders the emergence of germinating seeds.

The development of Xanthophyceae is driven by high surface moisture, high light intensity, and the presence of residual mineral fertilizers. Excessive nitrogen and phosphorus on the surface provide the necessary nutrients for rapid proliferation, leading to a visible bloom that quickly covers the substrate.

The economic impact of these algae includes stunted plant growth, reduced seed germination rates, and increased susceptibility to secondary fungal pathogens. By altering the soil micro-environment, they create a habitat that encourages damping-off and other soil-borne diseases, necessitating prompt remedial action.

• Frequent light cultivation or hoeing to break the surface crust.
• Optimizing irrigation schedules to ensure surface drying between cycles.
• Improving greenhouse ventilation to reduce relative humidity.
• Using mulch layers to block light penetration to the soil surface.
• Monitoring fertilizer application rates to prevent surface accumulation.