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Chemotherapy of Smut and Rust Pathogens in Poa pratensis by Thiazole Compounds. John R. Hardison, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, and Department of Botany and Plant Pathology, Oregon Agricultural Experiment Station, Corvallis 97331; Phytopathology 61:1396-1399. Accepted for publication 2 July 1971. DOI: 10.1094/Phyto-61-1396.

Five proprietary thiazole compounds were evaluated for systemic fungicidal properties against Ustilago striiformis (stripe smut), Urocystis agropyri (flag smut), and Puccinia striiformis (stripe rust) after soil application and root uptake in diseased Poa pratensis ‘Merion’. The parent thiazole compound, 2,4-Dimethyl-5-carboxanilidothiazole, eradicated U. striiformis and U. agropyri, and gave good control of P. striiformis. A 2-amino substitution on the parent thiazole heterocycle increased activity against both smuts and maintained good rust control. A 2-methyl substitution on the phenyl ring with an unaltered thiazole failed to control stripe smut, but maintained good control of flag smut and rust. A 2-amino substitution on the thiazole heterocycle plus either a 3-methyl or a 3-methoxy substitution on the phenyl ring seriously impaired activity against all three diseases, although phytotoxicity was reduced. The parent compound and the 2-amino substitution analogue were more active against U. striiformis and more phytotoxic than a related oxathiin compound, oxycarboxin. The thiazole compounds were inferior to oxycarboxin for control of flag smut and stripe rust.