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Aerobiology of Two Peanut Leafspot Fungi. D. H. Smith, Assistant Professor, Department of Plant Pathology, University of Georgia, College of Agriculture Experiment Stations, Georgia Station, Experiment 30212; F. L. Crosby, Agricultural Meteorologist, NOAA, National Weather Service, Georgia Station, Experiment, Present address: USDC, NOAA, Federal State Agricultural Weather Service, Lakeland, Florida 33802. Phytopathology 63:703-707. Accepted for publication 18 December 1972. DOI: 10.1094/Phyto-63-703.

Air was sampled continuously for fungal spores with a Hirst spore trap 0.5 m above a peanut (Arachis hypogaea) field during the growing seasons of 1969, 1970, and 1971. Low concentrations (spores per m³ of air per 24-hr period) of Cercospora arachidicola conidia and Leptosphaerulina crassiasca ascospores were present until mid-July during all 3 years. On days without rain, peak catches of L. crassiasca ascospores occurred within 1 to 4 hr after sunrise, when air temperature was rising and foliage was drying, while the number of C. arachidicola conidia increased rapidly after the termination of leaf wetness, with daily peak catches ranging from 1100 to 1500 hr. On days with rain, concentrations of C. arachidicola conidia and L. crassiasca ascospores increased rapidly with the onset of rainfall. The peak concentration of C. arachidicola conidia (> 300 per m³ of air) occurred from 3 to 4 September 1970, and the peak concentration of L. crassiasca ascospores (> 1,300 per m³ of air) occurred from 23 to 24 August 1970. Very few (< 1%) phragmosporous ascospores were trapped during the study. Evidence for vertical dissemination of C. arachidicola conidia to heights of 2.7 m (9 ft) was obtained by exposing healthy test plants in the field for brief periods of time. The number of C. arachidicola lesions on test plants decreased as exposure height increased.