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Leaf Spot Control, Maneb, and Ethylenethiourea Residues in Processed Turnip Greens Treated with Maneb. Donald R. Sumner and Durham K. Bell, University of Georgia, Department of Plant Pathology, Coastal Plain Experiment Station, Tifton 31793-0748; Dorris A. Lillard and William C. Hurst, Department of Food Science, and Parshall A. Bush, Department of Poultry Science, Athens 30602; and T. B. Brenneman, Department of Plant Pathology, Coastal Plain Experiment Station, Tifton 31793-0748. Plant Dis. 75:878-882. Accepted for publication 1 March 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0878.

Turnip leafy greens were grown in the spring and fall for processing into frozen greens. Maneb + zinc (1.8 or 0.9 kg a.i./ha), benomyl, chlorothalonil, or iprodione were applied weekly until 10 days before greens were harvested. Greens either sprayed with maneb + zinc or not sprayed were processed by washing with water (pH 6.76.9), 0.1% detergent (pH 6.76.9), or alkaline detergent (pH 9.79.9). All fungicide treatments reduced foliage disease induced by Pseudocercosporella capsellae. Reflectance data with a multispectral radiometer indicated no differences among fungicide treatments, and reflectance was negatively correlated with visual disease ratings and positively correlated with the percentage of leafy greens acceptable for processing. All methods of washing leafy greens sprayed with 1.8 or 0.9 kg a.i./ha of maneb + zinc reduced maneb but not ethylenethiourea (ETU) levels compared with unwashed greens. Cooking reduced maneb but not ETU levels compared with raw greens. There were no differences in ETU residues in greens between the two application rates of maneb + zinc. ETU residues were usually below 0.1 ppm in cooked greens in all treatments.