Rhabdonematales

Rhabdonematales represent an order of diatom algae that can function as opportunistic epiphytes or pathogens in specific agricultural settings. While primarily classified within phycology, their uncontrolled growth on the surface of aquatic crops constitutes a pathological condition that significantly impairs the health of the host plant.

The causal agents are colonial diatoms that attach to submerged plant surfaces. The type of damage is characterized as surface colonization, which acts as a barrier. By forming dense layers of frustules, these organisms obstruct light absorption and hinder essential gas exchange, causing chronic stress and growth retardation in affected crops.

The primary crops affected by Rhabdonematales are those cultivated in aquatic environments, such as rice paddies or hydroponic systems. The pathogen prefers the submerged portions of the plant, where it establishes stable colonies that can eventually cover the entire stem and leaf surface, creating a distinct yellowish or brown film.

Conditions favorable for the development and spread of Rhabdonematales include high water humidity, excessive nutrient loading (particularly nitrates and phosphates), and stable water temperatures within the range of 15°C to 25°C. Stagnant water bodies without proper aeration provide the perfect substrate for rapid colonization.

The economic impact of this infestation is significant, leading to reduced photosynthetic efficiency and diminished yield. Management and prevention strategies include implementing water circulation systems, monitoring nutrient runoff, utilizing biological controls, and applying approved algaecides to manage population density without causing phytotoxicity to the crop.