Coscinodiscaceae algae

In phytopathology, the infestation of higher plants by algae is considered a secondary process. Coscinodiscaceae are not obligate parasites, but their mass development in aquatic environments or on waterlogged substrates leads to mechanical and chemical impact on crop tissues.

The disease type is classified as an algosis. A key feature is the ability of algal cells, which possess rigid siliceous frustules, to penetrate intercellular spaces or settle on leaf and stem surfaces under conditions of excessive moisture.

The pathogen spreads primarily through irrigation water or during field flooding. Their high adaptability to various light levels allows them to colonize moist surfaces rapidly.

These microorganisms have a characteristic disc-like shape, which facilitates their attachment to the plant epidermis during the formation of biofilms in conditions of constant moisture.

The main sign of algal growth on the surface of vegetative organs is the formation of a specific coating, ranging from brown to grey-green in color.

When infested with Coscinodiscaceae algae, leaf surfaces may become rough or covered with a thin siliceous film, which hinders the normal gas exchange of the plant.

In the affected areas, transpiration processes are disrupted. Plants look stunted, growth slows down, and leaves may acquire a chlorotic hue due to a lack of sunlight.

In the early stages of colonization, the signs may resemble a superficial layer of dust, but upon inspection under magnification, a structured colony of microorganisms becomes visible.

• Discoloration of the epidermis to a brownish shade.
• Stomatal blockage by siliceous frustules.
• Reduction in photosynthesis intensity.
• Deformation of young shoots during heavy infestation.

The primary factor for development is prolonged waterlogging of the soil and water stagnation on leaf surfaces. Coscinodiscaceae thrive in conditions of high humidity and adequate mineral salt levels.

Temperature plays a secondary role, but moderately warm conditions promote rapid cell division in algae, which accelerates the biofilm formation process.

Poor ventilation in greenhouses or dense plantings in open fields create an ideal microclimate for the reproduction of these organisms due to the lack of rapid moisture evaporation.

Contamination of irrigation systems from open reservoirs containing phytoplankton is the primary source of infection for agricultural plots.

Reduced lighting contributes to changes in plant metabolism, making tissues more susceptible to the attachment of diatomaceous algae and subsequent colonization.

The harmfulness of Coscinodiscaceae algae lies in the mechanical shielding of the leaf surface, which blocks light access to chloroplasts and reduces photosynthetic productivity.

The siliceous frustules of these organisms can create a barrier to transpiration, leading to physiological imbalance and overheating of the leaf blade in sunny weather.

The constant presence of algae on the plant surface promotes the retention of excess moisture, which provokes the development of secondary fungal and bacterial infections.

In agricultural practice, mass infestation leads to a reduction in product quality, loss of turgor, and, in critical cases, the death of affected tissues.

Economic damage is associated not only with direct plant impact but also with costs incurred from additional protective measures required to clean plant surfaces.

The primary defense strategy is based on optimizing humidity. Strict control of irrigation is necessary to prevent water stagnation on leaves and the topsoil layer.

In greenhouses, effective ventilation and air circulation are mandatory, as they allow for lowering the relative humidity below the critical level for algal development.

To prevent the spread of the pathogen, it is recommended to use water filtration for irrigation from open reservoirs where the concentration of diatomaceous algae may be high.

The application of copper-based fungicides or specialized algaecides allows for effective suppression of algal development in the initial stages without significant harm to crops.

Agronomic measures include regular soil cultivation to improve aeration and the removal of heavily infested plant debris, which can serve as a reservoir for algal spore accumulation.