Air dispersal of conidia of Monilinia fructicola in peach orchards

Abstract

Air dispersal was found to be an important means of disseminating conidia of Monilinia fructicola. In the Murrumbidgee Irrigation Areas of New South Wales only one major dispersal period occurred in each of the four years of this study. This period commenced about one month before peach harvest and continued for about two months after harvest. Greatest numbers of conidia were trapped in seasons when rain fell about harvest time. Conidial concentrations were related to the number of fruit infections present. Diurnal periodicity in spore concentration was noted, the maximum concentration of air-borne spores usually occurring in early afternoon. There was wide variation in the number of conidia present in air at different sites within orchards at a given time. Conidia could be detected in air up to 300 feet from a source orchard, but not beyond this in the one test where this point was examined. Rainfall, humidity, windspeed, temperature, and dew records were compared with concurrent spore trappings, and possible relationships noted. The practical significance of the results is discussed in relation to chemical control and the culture of varieties of differing maturity.