Risk Analysis And Management Of Rice Stripe Disease Epidemics

Rice stripe disease caused by Rice stripe virus(RSV)is one of the most important diseases in East Asia,causing great grain loss thereby threatening rice production and global food security.The disease has caused several major epidemics in many countries including Japan,China,South Korea,North Korea and the Ukraine.The resurgence disease induced greater damage compared to its pre-2000 outbreaks,especially in Jiangsu Province,China.To control the disease epidemics from 2001,an abundance of labor,material and financial resources were input in Jiangsu Province.However,the disease epidemics still last more than 10 years.Unlike studies of RSV epidemics in the 1960-1970s,in the current experiments co-incident with the current upsurge in RSV,we established a set of sprayed and unsprayed fields in 8 counties in Jiangsu Province where disease,RSV,its vector insect(Laodelphax striatellus,small brown planthopper,SBPH),climatic conditions and human factors were monitored between 2002 and 2012.Disease data gathered from both sprayed and unsprayed fields over a 10-year period of epidemics were evaluated by statistic methods such as Spearman correlation to determine key biotic and abiotic factors driving epidemics of the disease in parallel with the data of vector,climatic and human factors with an objective to develop a lower cost,more effective and ecologically friendly approach for managing RSV and other plant disease.The result is expected to lead the development of theory and practice of plant disease managment.Disease severity of RSV was positively correlated with viruliferous rate of the vector but not with the population density of the insect,suggesting that,the proportion of vectors infected by the virus rather than the absolute number,plays an important role in RSV epidemics and could be used for disease forecasting.This result also suggests that viruliferous rate could be a good indicator of RSV disease epidemics and management such that the equation In(y·100)=4.2-0.1861/x,[where y is the expected disease severity and x is the viruliferous rate of overwintering SBPH]could be used for disease forecasting.The finding of a positive correlation of disease severity and viruliferous rate among years suggests that local infection is likely the main source of primary inoculum of RSV.Of the two main climatic factors,temperature plays a more important role than rainfall in RSV epidemics.In unsprayed and sprayed fields,rice stripe disease severity in any given year was correlated with the time gap between wheat sowing and rice harvest in preceding year and between rice sowing and wheat harvest in current year,suggesting that,the time arrangement of wheat and rice production is related to the disease epidemic.The time gap between wheat sowing and rice harvest was correlated with viruliferous rate but not with the total and viruliferous population density of the overwintering and first generation of SBPH in following year.These results suggest that the rotation system of rice and wheat cteated the environment to maintain SBPH viruliferous rate in wheat field and then turned to the primary inoculum of RSV from wheat to rice.The finding of a negative correlation between the total rice resistant level in every county and disease severity of current year,and overwintering SBPH viruliferous rate of following year suggest that lower rice resistance plays a role in higher SBPH viruliferous rate of following year which resulted in the following RSV epidemics.Compared with the rice resistance,the cropping system adjustment of rice and wheat may reduce the RSV epidemic degree gradually at the late-stage.Future plant disease management including rice stripe disease should aim to strengthen food security for a stable society while simultaneously safeguarding the health of associated ecosystems and reducing dependency on natural resources.To achieve these multiple functionalities,sustainable plant disease management should place emphases on rational adaptation of resistance,avoidance,elimination and remediation strategies individually and collectively,guided by traits of specific host-pathogen associations using evolutionary ecology principles to create environmental(biotic and abiotic)conditions favorable for host growth and development while adverse to pathogen reproduction and evolution.Plant disease management plays an important role in food security,economic improvement and social stability.However,the technologies available are often limited as a result of conflicting interests between producers and society,a lack of understanding of economic thresholds,and the complex interactions among ecology,productivity and profitability.A comprehensive evaluation of economic,societal and ecological effects with technologies and production demands as main components should be used to guide approaches for sustainable disease management that aim to mitigate crop loss while maintaining functional farm ecologies and biodiversity.Consequently,there should be an increased emphasis on technology development,public education and information exchange among governments,researchers,producers and consumers to broaden the options for disease management in the future.