Aerodynamic diameter of conidia of Alternaria species

The aerodynamic diameters of conidia of five species of Alternaria and Stemphylium botryosum were estimated using an inertial impaction method based on a May Ultimate Impactor. The same technique was used to estimate the aerodynamic diameter of unidentified Alternaria species collected from an oilseed rape crop. Aerodynamic diameters tended to increase with spore length or diameter and ranged from about 10 to 40 mum, although spore length ranged from about 10 to 220 mum. It was also found that the aerodynamic diameter, and therefore the fall speed of Alternaria-like spores, can be estimated from cylinders of unit density and the same length and mean diameter of the spores.