Fragilariaceae algae

Fragilariaceae represent a family of diatomaceous algae that can act as a significant stress factor in modern agricultural practices, particularly in systems where water management is critical, such as hydroponics or paddy rice fields. While not typically classified as classic plant pathogens, their proliferation interferes with normal plant physiological processes.

The biological nature of this concern lies in the algae's ability to form dense colonial mats or biofilms. These structures create a physical barrier on the surface of growing media or in aqueous nutrient solutions, which significantly reduces the dissolved oxygen concentration and prevents essential gas exchange for the root systems of crops.

The primary crops affected by the unchecked growth of these algae are paddy rice during flooding stages and various horticultural crops grown in hydroponic or aquaponic systems. These organisms rapidly utilize available mineral nutrients, effectively starving the crop plants and leading to nutrient deficiencies despite sufficient fertilizer application.

Symptoms of infestation are identified by the presence of yellowish, brown, or brownish-green slimy coatings on roots, irrigation pipes, or the surface of growing substrates. Affected plants often exhibit stunted growth, chlorosis, and root system degradation due to oxygen deprivation, which makes them more susceptible to subsequent opportunistic fungal infections.

Control strategies for Fragilariaceae focus on environmental manipulation rather than eradication. Key measures include:

• Optimization of nutrient solution concentrations to limit excessive algae feeding.
• Implementation of robust aeration systems to increase dissolved oxygen levels.
• Management of light exposure to prevent photosynthetic activity of the algae.
• Use of certified algicides or biological control agents in closed-loop systems.
• Strict sanitation and disinfection of reservoir tanks and delivery lines.