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Systemic Fungicidal Effect of Thiophanate Methyl on Verticillium Wilt of Cotton and Its Transformation to Methyl 2-Benzimidazolecarbamate in Cotton Plants. H. Buchenauer, Department of Plant Pathology, University of California, Riverside 92502, Present address of senior author: Institut für Phytopathologie und Pflanzenschutz, University of Hohenheim, 7000 Stuttgart 70, W. Germany; D. C. Erwin(2), and N. T. Keen(3). (2)(3)Department of Plant Pathology, University of California, Riverside 92502. Phytopathology 63:1091-1095. Accepted for publication 5 February 1973. DOI: 10.1094/Phyto-63-1091.

Soil treatment with the systemic fungicide 1,2-bis(3-methoxycarbonyl-2-thioureido) benzene (thiophanate methyl or TPM) prevented foliar symptoms and vascular discoloration of cotton plants caused by subsequent stem inoculation with Verticillium albo-atrum. Foliar treatment with TPM was less effective against Verticillium wilt than treatment with the hydrochloride salt of methyl 2-benzimidazolecarbamate (MBC·HCl). When roots were allowed to take up TPM for 1 day, the foliage contained not only TPM but also another fungitoxic compound which was isolated and identified as MBC. After 6 days, nearly all of the TPM had been converted to MBC. TPM was more rapidly converted to MBC in akaline than in acidic solutions in vitro. The growth of Verticillium was inhibited more by MBC than by TPM, but more TPM than MBC was taken up by the foliage of cotton plants. However, MBC·HCl was taken up more readily than either MBC or TPM. Small amounts of TPM were detectable below the area of foliar application but only in the bark tissue.