Pathogeographic studies of sugarcane downy mildew in TAIWAN.(I) Historical analysis, regional pathogeographic classification and some considerations of disease attributes of the epidemics

Abstract

The pathogeographic history of sugarcane downy mildew in Taiwan was traced from 1909 to 1978. Three major epidemic periods were distinguished: namely, 1955-57, 1965 and 1973. Geographic distribution of the disease was also mapped. Hsinying area was identified as the primary disease focus and Pingtung area, the secondary disease focus. Areas of main damage, marginal damage, sporadic attack as well as nonepidemic region were distinguished. By means of cluster analysis based on three disease attributes (disease frequency, intensity and extensity), a pathogeographic classification of the sugarcane factory districts in Taiwan was presented. The classification corresponds with the disease regions demarcated in the geographic studies. Correlation of the spatial and temporal attributes (disease intensity, extensity, frequency and duration) was found and the meaning of such correlation was discussed.