Euglenophyceae

The primary visual sign is the formation of a bright green or emerald-coloured film on the soil surface. This film typically appears as a slimy or shiny layer that spreads across moist substrates.

As the surface dries, the algae layer can harden into a crust. This crust acts as a physical barrier that restricts oxygen exchange between the soil and the air, negatively impacting root respiration.

In hydroponic setups, the infestation manifests as green slime on tubes, emitters, and reservoir walls. The nutrient solution itself may become tinted with green pigment, indicating high algal density.

Plants affected by these colonies often show stunted growth, leaf yellowing, and a weakened root system. The presence of algae around the root collar can lead to decay and wilting.

Seedlings are particularly vulnerable; they may collapse if the algal film prevents adequate aeration and traps excessive moisture against the delicate stem.

The causative agents are unicellular algae known as Euglenophyceae, which belong to the group of flagellates. In agronomic terms, they act as undesirable biological contaminants that disrupt the stability of the plant substrate.

These organisms are mixotrophic, meaning they can perform photosynthesis in the presence of light and absorb organic matter in the dark. This dual survival strategy allows them to thrive in diverse agricultural environments.

Reproduction occurs through cell division, leading to rapid colonisation of substrate surfaces and irrigation systems. While not obligate parasites, their rapid proliferation can suffocate young plants and seedlings.

In greenhouses, these algae are often introduced via untreated irrigation water or contaminated organic media. Their resilience makes them a persistent challenge for plant production systems.

By altering the chemistry and pH of the rhizosphere, these algae can indirectly affect nutrient uptake, creating an unfavourable environment for the crop's development.

The development of Euglenophyceae is primarily driven by high moisture levels and constant light exposure. Direct sunlight or intensive greenhouse lighting significantly accelerates their growth.

Excessive use of nitrogen and phosphorus-based fertilisers provides abundant nutrients, promoting explosive growth of the algae. They outcompete the crop for essential minerals.

Poor ventilation and high relative humidity in greenhouses create an ideal microclimate for algal proliferation. They typically thrive at temperatures between 20 and 28 degrees Celsius.

Irrigation with water from open reservoirs often introduces these algae into the growing area. Furthermore, non-sterile peat or compost substrates can harbour spores or dormant cells.

The lack of mulch or surface cover allows light to reach the soil, which triggers the photosynthetic phase of the algae and ensures their rapid colonisation of the pot surface.

The main harm is the creation of an airtight barrier on the soil surface, leading to hypoxia (oxygen starvation) in the root zone. This causes root hair dieback and weakens the overall plant structure.

Algae compete directly with crops for nutrition. By consuming fertilizers intended for the plants, they reduce yield efficiency and can lead to nutrient deficiencies in the cultivated species.

In hydroponics, algal slime causes physical obstruction in filters, nozzles, and drip systems, leading to uneven nutrient distribution and potential failure of irrigation infrastructure.

Excessive moisture trapped by the algal mats promotes the development of secondary pathogens, including root rot fungi, which can cause significant crop losses.

Finally, the presence of green slime degrades the aesthetic quality of ornamental plants and nursery stock, negatively impacting their market value and shelf appeal.

The most effective cultural control is regular surface cultivation. Loosening the topsoil disrupts the algal film and restores essential aeration to the roots.

Mulching the soil surface with gravel, clay pellets, or opaque covers is a highly effective strategy. By blocking light, you inhibit the photosynthetic activity necessary for the algae to survive.

Proper irrigation management is critical. Avoid overwatering and ensure that fertilizer concentrations are strictly adhered to, reducing the nutrient surplus that fuels algal growth.

In cases of severe hydroponic infestation, disinfection of the system with hydrogen peroxide or registered algaecides is necessary to eliminate the pathogen without harming the plants.

• Improve greenhouse ventilation to reduce surface moisture.
• Use sterilized substrates and high-quality certified growing media.
• Implement preventive treatment with safe, biological fungicides.
• Filter irrigation water to remove algal spores before delivery.