Rice false smut

The disease known as Rice false smut is caused by the fungus Ustilaginoidea virens (teleomorph Villosiclava virens). It is a significant fungal infection that specifically targets rice crops, interfering with grain development and causing substantial losses in agricultural productivity globally.

The primary symptom of the disease is the transformation of individual rice kernels into large, velvet-like spore balls. Initially, these structures appear as orange or yellowish masses protruding from the glumes, eventually maturing into dark green or black powdery masses containing fungal chlamydospores.

The development of Ustilaginoidea virens is highly dependent on environmental factors. Prolonged high relative humidity (above 85%) and rainy weather during the flowering or heading stage of the rice plants significantly increase the susceptibility of the crop to infection by airborne spores.

False smut is not only a quantitative threat to yield but also a qualitative one. The fungus produces mycotoxins, specifically ustilaginoins, which pose health risks to both humans and livestock. Consequently, contaminated rice batches are often rejected or devalued, leading to severe economic implications for producers.

Integrated pest management (IPM) is the most effective approach to control this pathogen. This includes the implementation of balanced nitrogen fertilization to avoid excessive vegetative growth, the use of certified disease-free seeds, and the application of systemic fungicides at the early booting stage to protect the vulnerable panicles from infection.