No abstract

Recently, a heavy outbreak of Japanese pear rust caused by Gymnosporangium asiaticum developed in Fukuoka Prefecture, Japan. We carried out a retrospective cohort study of commercial orchards in Yame region to analyze the reason. Among the factors investigated, the use of non-sterol-demethylation-inhibitor (non-DMI) fungicides was only related to extent of disease severity in 2013 and disease incidence in 2014. However, DMI fungicides did not control rust well. These results suggested the possibility that DMI fungicide resistance developed in G. asiaticum populations there. Furthermore, our results indicated that retrospective cohort study is useful for the analysis of occurrence factors on plant diseases.