Deposition of Erysiphe graminis Conidia on a Barley Crop

Abstract Naturally released Erysiphe graminis conidia were trapped (on horizontal slides, on vertical sticky cylinders and in suction traps) in a barley crop infected with powdery mildew and the numbers of single spores and of clumps of different sizes deposited on the traps were counted. The efficiencies of impaction calculated from deposits and wind speed measurements were higher than expected from mean wind speed measurements. The values were consistent with the hypothesis that spores were removedpredominantly in gusts. More than half the conidia were removed in clumps of two or more spores. The measurements suggest that clumps were more effectively deposited than single spores. The measurements demonstrate that spore release mechanisms can influence spore deposition significantly, especially close to the source.