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Vertical Spore Concentrations of Three Wheat Pathogens Above a Wheat Field. M. G. Eversmeyer, Research Technician, Plant Science Research Division, ARS, USDA, Manhattan, Kansas 66502; C. L. Kramer(2), and J. R. Burleigh(3). (2)Associate Professor, Division of Biology, Kansas State University, Manhattan, Kansas; (3)Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Manhattan, Kansas 66502. Phytopathology 63:211-218. Accepted for publication 5 March 1972. DOI: 10.1094/Phyto-63-211.

Kramer-Collins volumetric samplers were used to study vertical dispersal and dissemination of urediospores of Puccinia recondita and P. graminis, and conidia of Erysiphe graminis, above a source area in 1969 and 1970. Air within the canopy and at 1, 3, and 6 m above ground level was sampled to measure the hourly and daily variations in spore concentrations which were then related to variations in meteorological data obtained in the same field. Considerable daily and hourly variation in spore concentrations of the three species occurred within and above the wheat canopy. Circadian patterns with distinct diurnal maxima were noted in both years. However, variation in meteorological factors could cause rapid changes in spore concentrations, with peaks occurring any time during the day or night. Changes in wind velocity or turbulence accounted for most of the peaks observed in hourly spore concentrations. Higher wind velocities were required to dislodge spores when the foliage was wet or when pustules were located lower in the canopy. When spore concentrations and sampling height were plotted on logarithmic scales, the three species exhibited distinctly different spore profiles. These differences were attributed to exogenous P. graminis and to endogenous and exogenous P. recondita urediospores being trapped above the canopy, whereas the infected wheat canopy was the source of the E. graminis conidia. Profiles of spore concentrations at different heights can be used to distinguish between endogenous, exogenous, and mixed inoculum sources, and aid in positioning of samplers used in epidemiological studies.

Additional keywords: aerobiology, epidemiology.