Dry-seeded rice

Dry-seeded rice refers to an agronomic practice where rice seeds are sown directly into dry or moist soil without the traditional nursery stage or flooding. This method is gaining popularity globally due to its potential to save water and reduce the labor requirements associated with transplanting. However, it alters the environmental conditions significantly, making the crop susceptible to a different spectrum of pathogens.

From a phytopathological perspective, dry-seeded rice lacks the protective anaerobic environment provided by flooding, which typically inhibits several soil-borne diseases. Without this barrier, the crop is more prone to fungal infections, such as those caused by Rhizoctonia solani and various leaf spot pathogens that thrive in the fluctuating moisture conditions of dry or aerobic soil systems.

The biology of pathogen development in this system is characterized by rapid colonization of the seedling and root zones during the initial growth stages. Fungal spores present in crop residues or soil can easily infect the seeds or young tissues when the soil moisture is insufficient to stress the pathogen, yet high enough to allow mycelial growth. Temperature fluctuations in non-flooded fields further accelerate the life cycles of these organisms.

Environmental conditions, particularly soil moisture management, are critical for both crop development and disease suppression. When dry-seeded rice fields undergo periods of drought followed by irrigation, the plant experiences physiological stress. This stress lowers the natural defense mechanisms of the rice plants, facilitating opportunistic pathogen entry and leading to potential yield reductions across the entire field.

Integrated pest and disease management is essential for successful dry-seeded rice cultivation. Control strategies include using certified fungicide-treated seeds, implementing crop rotation to break pathogen cycles, and utilizing resistant rice varieties. Regular monitoring and timely application of fungicides are crucial, alongside weed management, as competing weeds can act as reservoirs for pathogens, further increasing the pressure on the rice crop.