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Geostatistical analysis of rice blast in China at three different scales

Fangfang Guo: China Agricultural University

<div>Blast caused by <em>Magnaporthe oryzae </em>is one of the most destructive diseases in rice worldwide. Knowledge on the spatial pattern of disease incidence is essential to understand its epidemic. In this study, spatial patterns of rice blast were analyzed using geostatistical tools at three different scales. At large-scale, rice blast incidences at 47 to 107 stations in major rice production regions in China were surveyed from 2009 to 2014. At middle-scale, 53, 151, 142 fields in an area of 190000, 60000, 1900000 hectares were surveyed at three locations in North of Jiangxi, South of Jiangxi, and the junction area of Jiangxi, Hubei, and Anhui Provinces, respectively. At small-scale, rice blast incidence was determined on grids within 3 fields each in Jiangxi and Liaoning Provinces. Results demonstrated that rice blast incidence exhibited significant spatial dependence with influence ranges from 398 to 1080 km on 10 dates out of the 101 survey dates. At middle-scale, a significant linear trend was detected in 2 out of the 3 locations, but no significant spatial dependence was observed. At small scale, strong spatial dependence with an influence range of 5 m was detected in one out of 3 fields in Jiangxi, while strong spatial dependence with an influence range of 7.2 to 10 m was detected in all the three fields in Liaoning. The findings from this study provide helpful information to sampling and management of rice blast.</div>