Management Options - Brown Spot

Varietal resistance

In areas where the disease is common and serious, the use of resistant varieties is the most economical means of control. Some anatomical features of rice leaves appear to relate to resistance. It was reported that thicker epidermal cells and more silicated cells are positively correlated with resistance. Increased susceptibility coincides with increased dry weight, total nitrogen, free amino acids, and total protein.

In India and the United States, resistant varieties grown either as direct-seeded or transplanted in both light and medium soil types were found to be resistant to brown spot.

Cultural practices

Providing proper nutrition for optimum plant growth and prevention of water stress seem to be the most important factors in controlling brown spot. This is due to the fact that the disease is rarely observed in normally fertile rice soils. Soils known to be low in plant-available silicon should be amended with calcium silicate slag before planting and the field should be well irrigated to avoid water stress.

Field practices such as sanitation, crop rotation, adjustment of planting date, and proper fertilization should also be practiced in areas where the disease is endemic. Since the fungus is seed transmitted, a hot water seed treatment (53-54°C) for 10-12 minutes before sowing is effective. This treatment controls primary infection at the seedling stage. Presoaking the seed in cold water for 8 hours increases the effectiveness of the treatment.

Chemical control

Some chemical seed treatments may be available to reduce the effects of brown spot on young plants and reduce some of the initial inoculum. In India, Grisepfulvin, nystatin, aureofungin, and similar antibiotics have been found effective in preventing primary seedling infection. Secondary airborne infections may also be controlled by spraying edifenphos, mancozeb, and propiconazole. However, field application of these fungicides may not always be economical.