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Influence of Tillage, Planting Date, Inoculum Survival, and Mixed Populations on Epidemiology of Southern Corn Leaf Blight. Donald R. Sumner and R. H. Littrell, Assistant Professors, Department of Plant Pathology, University of Georgia, Coastal Plain Station, Tifton 31794 Phytopathology 64:168-173.

Wholeplots of naturally infected corn residues were disk-harrowed, rotary-chopped, or plowed in November, 1970.  In 1971, corn with Texas male sterile cytoplasm (Tcms) and normal cytoplasm (Nc) was planted 18 March and 15 April.  There were significantly fewer southern corn leaf blight (SCLB) lesions on Tcms plants in plowed plots through 31 May when the early plants were beginning to tassel.  Corn planted 15 April had a greater number of lesions than that planted 18 March, regardless of treatment.  There was a highly significant negative correlation of number of SCLB lesions/subplot 21 May in both plantings and yield (r = -.46).  In other plots planted to blends of Tcms and Nc, yield losses were directly proportional to the percentage Tcms plants and the distance from inoculated Tcms plants.  Race T of Helminthosporium maydis survived in all residues from blends of Tcms and Nc, but it survived more abundantly in residues from Tcms plants.  Tcms and Nc were planted separately in either disked or plowed subplots of each mixture of residues in 1972.  There were significantly more lesions on Tcms plants in disked than in plowed subplots, but no significant differences in yields occurred.

Additional keywords: Phyllosticta, Colletotrichum graminicola, chlamydospores, dew period.