Effects of Protection Time on Infection of Rice Panicle Blast

Panicle blast, caused by Magnaporthe oryzae, is a destructive disease of rice worldwide. Clarifying the susceptibility of rice panicles at different stages is of great significance for effective disease management. Field experiments were conducted in two paddy fields at Wuyuan County in 2016 and 2017 to determine the effects of head covering and its timing on the infection of rice panicle blast. Results revealed that panicle blast was reduced significantly by covering rice heads with sulfuric acid paper bags, regardless of the covering time, ranging from initial heading to 15 days afterward, suggesting that rice panicles could be infected by blast pathogen even 15 days after initial heading. Panicle blast incidence was also found to be significantly influenced by plant dates, with higher panicle blast incidence observed in plots planted on early dates, suggesting adjusting plant dates could help rice panicles escape the infection by blast pathogen. The results from this study also highlighted the importance of cultivars and environmental conditions to panicle blast. In conclusion, besides planting blast-resistant cultivars, it is important to protect rice heads from the initial heading to the early dough stages, and fungicides should be applied according to infection warnings based on host, inoculum, and weather conditions.