Rice spikelet rot disease in China – 2. Pathogenicity tests, assessment of the importance of the disease, and preliminary evaluation of control options

In recent years, a rice panicle disease—rice spikelet rot, occurred seriously in large rice-growing area in China, causing the rice grains discolor, unfilled and deform. It does not only influence the rice yield, because of the colored pathogens and toxigenic, but also changes the appearance of the rice and reduces its quality. Spikelet rot disease influences on the rice production and market price, and causes harm to the safety and health of human and livestock. This paper makes effort to elucidate the occurrence, epidemic regularity of the disease, the pathogenicity of isolates. Fungicides to control the disease were preliminarily selected in lab and control efficiency test were conducted in field. The investigation results indicate that japonica varieties and their hybrid combination, tighten panicle varieties are easier to be infected by the disease than that of the indica rice varieties with loosen panicles. It was propitious to the disease occurrence and epidemic when rice late booting to flowering period met the overcast, rainy (high humidity) and warm (25–33 °C) climate. Indoor selection results showed that ketotriazole shows very good restraint effect on the pathogens. Seed treating with fungicide, spraying ketotriazole, carbendazim + thiram mixture or tricyclazole at later booting and/or flowering stage can reached over 70% control efficiency to the disease.