Rainfall conditions inducing the dispersion of conidia of Botryosphaeria berengeriana

Abstract

The conditions inducing the peak dispersion of conidia of Botryosphaeria berengeriana were investigated using data collected during eight periods of continuous rainfall between 1991 and 1992. These rainfall events varied from 800 to 1540 minutes in duration. Conidia were collected about every two hours onto 2 glass microscope slides coated with glycerol jelly using a spore trap. The spore trap was set up in the midst of some naturally infected pear prunings about 20 cm in length at the height of 1 m from the groundside. This monitoring clearly showed that at least three hours from the beginning of a rainfall episode was needed before a large number of conidia of Botryosphaeria berengeriana dispersed under continuous rainfall. Moreover, it was shown that 60% or more of the total number of conidia produced by a rainfall event were released in the total period of 4-6 hours before and after the peak. Clarifying the rainfall conditions that induce maximal dispersion of conidia will help in understanding and so preventing disease outbreaks.