Combined Biological and Chemical Seed Treatments for Control of Two Seedling Diseases of Sh2 Sweet Corn. D. E. Mathre, Department of Plant Pathology, Montana State University, Bozeman 59717. R. H. Johnston, Department of Plant Pathology, Montana State University, Bozeman 59717; N. W. Callan, Western Montana Ag Research Center, Corvallis 59828; S. K. Mohan, Idaho Research and Extension Center, Parma 83660; J. M. Martin, Department of Plant, Soil, and Environmental Science, Montana State University, Bozeman 59717, and J. B. Miller, Western Montana Ag Research Center, Corvallis 59828. PLANT DIS. 79:1145. Accepted for publication ll August 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1145.

Experiments were conducted in both the glasshouse and in the field lo determine if biological and chemical control agents could be used together on sweet corn (Zea mays L.) seed to control Pythium ultimum damping-off or Penicillium oxalicum seedling disease. Pseudomonas aureofaciens AB254 and Pseudomonas sp. AB842 were used for control of P. ultimum and P. oxalicum, respectively. Metalaxyl seed treatment for control of P. ultimum was used at rates from 100 to 0.01% of the recommended rate either alone or in combination with P. aureofaciens AB254. Imazalil seed treatment for control of P. oxalicum was used at rates from 100 to 1 % of the recommended rate either alone or in combination with Pseudomonas sp. AB842. In field tests, combining a chemical treatment with the biological agent did not affect the efficacy of disease control. Nor did combining low rates of chemical with the biocontrol agent increase the efficacy or reliability of disease control.