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The Effect of Concentration, Exposure Time and Age of Plant on Uptake and Translocation of Two Systemic Fungicides in Soybeans. B. L. Kirkpatrick, Former Graduate Research Fellow, Department of Plant Pathology, University of Illinois, Urbana 61801, Senior authorís present address: Department of Botany, University of Illinois, Urbana 61801; J. B. Sinclair, Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 66:102-105. Accepted for publication 20 July 1975. DOI: 10.1094/Phyto-66-102.

When soybean (Glycine max) tissues were bioassayed by an agar diffusion method against Penicillium atrovenetum, the size of zones of inhibition was greater following a 24-hour root exposure to BD 18654 and thiophanate-methyl (TM) than with a 12-hour exposure. Thiophanate-methyl breaks down into methyl 2-benzimidazole-carbamate (MBC). Inhibition zones were greater around all tissues, except cotyledons, from seedlings treated with BD 18654 than TM. The higher the concentration of BD 18654 used, the greater the zones of inhibition for all tissue samples, except those from trifoliolate leaves of 2-week-old seedlings. Increased concentrations of TM resulted in greater zones of inhibition only from hypocotyl tissues. Bioassays showed that the two fungicides were absorbed through the roots of 1- and 2-week-old seedlings, were translocated, and became more or less evenly distributed to all aboveground parts. The roots of seedlings exposed to the two fungicides for 24 hours were protected for 1 week against Macrophomina phaseolina.

Additional keywords: charcoal rot, Rhizoctonia bataticola.