VIEW ARTICLE

Disease Control and Pest Management

Use of an Action Threshold for Common Maize Rust to Reduce Crop Loss in Sweet Corn. H. R. Dillard, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, 14456; R. C. Seem, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, 14456. Phytopathology 80:846-849. Accepted for publication 14 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-846.

An action threshold of 80% incidence, based on incidence and severity relationships for common maize rust on sweet corn caused by Puccinia sorghi, was evaluated in commercial plantings of sweet corn grown for processing in central and western New York. Three different plantings of the cultivar Jubilee were evaluated each year from 1986 through 1988. Applications of mancozeb made at or near the action threshold resulted in significantly reduced disease severity (measured as percent leaf area diseased) at harvest and a significant reduction in the area under the disease progress curve in most fields. The mean number of marketable ears harvested, green weight of the ears, and the husked ear weight were significantly greater in mancozeb-treated blocks in most fields. The 80% incidence action threshold can be used as a guideline for proper timing of the first fungicide application, which is critical for preventing development of damaging levels of disease.