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Benomyl for Practical Control of Dutch Elm Disease. E. B. Smalley, Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706; C. J. Meyers(2), R. N. Johnson(3), B. C. Fluke(4), and R. Vieau(5). (2)Research Specialist, Department of Plant Pathology, University of Wisconsin, Madison 53706; (3)Village Forester, Village of River Hills, 7650 N. Pheasant Lane, Milwaukee 53217; (4)Forestry Technician, Department of Public Works, Bureau of Forestry, City of Milwaukee, Milwaukee 53202; (5)City Forester, 201 Delafield Street, Waukesha 53186. Phytopathology 63:1239-1252. Accepted for publication 26 March 1973. DOI: 10.1094/Phyto-63-1239.

Remission of naturally or artificially induced Dutch elm disease in its early stages was achieved in a high percentage of elms treated by trunk or soil injection with benomyl, methyl 1-(butylcarbamoyl)-2-benzimidazole-carbamate. Early, fast-developing infections, such as occur with root graft transmissions or recurrent disease were not controlled by such treatments except in cases of recurrent disease where treatment was combined with removal of the infected branches. Mass protection was achieved in municipal situations by spring application of benomyl either by trunk injection or by mist-blown foliar sprays. In such treatments, the incidence of new infection in untreated trees was 3 to 4 times greater than in the treated trees. Analysis and bioassay of greenhouse-grown elms sprayed with benomyl formulations suggested that systemic uptake of benomyl was accomplished in small branches through the lenticels. Improved solubilization of the benomyl without phytotoxicity was achieved using acetone-HCl solutions and in suspension with Tween 80, polyoxyethylene sorbitan monoleate, and Tergitol NPX, polyglycol ethers. Lactic acid solubilization yielded high antifungal activity, but solutions were extremely phytotoxic.

Additional keywords: Benlate, systemic fungicide, translocation, Ulmus americana, Ceratocystis ulmi.