The dispersal of spores of B. cinerea has been studied in a raspberry plantation at Invergowrie over years. Spores are released from the conidiophores by a hygroscopic mechanism and are then dispersed by air currents or rain splash. Maximum airborne spore concentrations occur when the relative humidity is rising or falling rapidly between the approximate limits 65-85%, but rainfall often induces dispersal at other times. Concentrations depend on the amount of sporulating material available, which in turn depends on temperature, humidity, the magnitude of previous dispersals and on the stage of development of the crop, since generally only ripe fruit and freshly exposed receptacles support sporulation. Levels of the order of 104 spores/m.3 of air have been recorded frequently during the fruiting period.
The implications of the dispersal mechanisms in relation to disease control are discussed.