The Effect of Temperature and Period of High Relative Humidity on Appearance of Bacterial Leaf Spot of Hydrangea Caused by Acidovorax valerianellae

Abstract

Bacterial leaf spot by Acidovorax valerianellae is a serious disease for potted hydrangea production in Gunma Prefecture. The effect of temperature and period of high relative humidity on appearance of bacterial leaf spot of hydrangea was investigated. The disease incidence of hydropore at 20℃ and 25℃ were 27.2% and 31.2%, respectively. These incidences were significantly higher than those of 10℃ and 15℃. At 20℃ and 25℃, the disease incidence increased under high relative humidity condition for more than 2 days.