Pathogeographic studies of sugarcane downy mildew in TAIWAN. II. A preliminary characterization of host factors in four pathogeographic regions.

Abstract

The disease and host attributes of four different pathogeographic regions from 1965-1978 were compared. The regions studied were Taichung (nonepidemic region), Huwey (sporadic region), Hsinying (region of main damage) and Pingtung (region of marginal damage). The disease attributes studied were disease intensity, extensity, frequency and duration. The host attributes were planting acreage of sugarcane and corn, the ratio of the two; ratio of disease-conducive varieties planted and disease potential index of the sugarcane population; the ratio of susceptible and resistant corn varieties and the practice of corn interplanting. Good correlation was found with the ratio of disease-conducive sugarcane variety, the disease potential index of the sugarcane population and disease incidence on sugarcane. Failure to find correlation with disease on sugarcane and the corn host population is probably due to the inadequacy of the historical data of corn. The host factors accounting for the different levels of disease intensities in the different pathogeographic regions were also discussed.