P-240 - Meteorological factor analysis utilizing the state-space model on the occurrence of red crown rot of soybean in Japan

Red crown rot (RCR), caused by Calonectria ilicicola, is one of the major soil-borne diseases of soybean. In RCR, the pathogen can infect soybean plants at early stages, even 2 weeks after sowing. However, symptoms tend to manifest after the flowering stage. Various cultivation and meteorological factors have been thought to influence the progression from infection to disease onset over several months. Those effects on the progression were analyzed using a state-space Bayesian model with a time-series structure. The response variable in the model was the RCR disease rate in 242 fields located in Akita, Fukushima, and Niigata Prefectures, Japan, from 2010 to 2012 and 2015 to 2018. Explanatory variables included precipitation; average temperature in June, July, and August of each investigated year; and cultivation factors previously identified as influencing RCR occurrence. The analysis revealed that in addition to cultivation factors, meteorological conditions significantly contributed to disease occurrence. Specifically, high temperatures and low precipitation during August and heavy rainfall during July were identified as factors promoting RCR occurrence in the surveyed fields. Although RCR prevalance is generally elevated in high rainfall conditions, these findings suggested that environmental conditions such as high temperatures and low precipitation during the reproductive stage may also enhance disease development.