Abstract
Yearly fluctuation patterns of the occurrence of false smut in paddy fields in Ibaraki Prefecture were analyzed by Principal Component Analysis, using as variables the percentages of diseased plants in the 7 years from 1988 to 1994. The analysis showed that the first principal component was related to the disease abundance and the second to yearly fluctuation patterns. We classified the whole area of Ibaraki Prefecture into 8 different regions in which the patterns of yearly disease occurrence differed from each other based on the score values of the first and second components at each of 150 fields. These classifications will be invaluable for forecasting the occurrence of this disease.
