VIEW ARTICLE

Disease Control and Pest Management

Translocation of Metalaxyl in Soybean Plants and Control of Stem Rot Caused by Phytophthora megasperma f. sp. glycinea. J. P. Gupta, Department of Plant Pathology, University of California, Riverside 92521; D. C. Erwin(2), J. W. Eckert(3), and A. I. Zaki(4). (2)(3)(4)Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 75:865-869. Accepted for publication 11 March 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-865.

Metalaxyl, applied to seeds, leaves, cotyledons, and soil, was translocated mainly in an upward direction in soybean plants. Treatment of seeds with metalaxyl resulted in partial control (40% survival) at 30 mg/100g of seeds and complete control (100% survival) at 200 mg/100 g of seeds of stem rot when wounded hypocotyls of 7-day-old plants were inoculated with Phytophthora megasperma f. sp. glycinea. The percentage distribution of metalaxyl (measured by gas chromatography) in 7-day-old plants after seed dressing (200 mg/100 g of seeds) was 79.2% in the cotyledons, 20.3% in leaves and stems, and less than 0.12% in roots. When ¹⁴C-metalaxyl (48.7 x 10⁴ dpm per seed) was applied to seeds, 91.5% of the extractable radioactivity (metalaxyl and derivatives) in 7-day-old plants was detected in the cotyledons, 5.8% in leaves and stems, and 2.57% in roots. The extract of cotyledons from 7-day-old plants treated at 200 mg/100 g of seeds and assayed by thin-layer chromatography, contained 40% ¹⁴C metalaxyl, while 60% of the radioactivity remained at the origin of the chromatogram. When ¹⁴C-metalaxyl was applied to a leaf or to a cotyledon, 99% of the recovered radioactivity remained in the treated leaf or cotyledon. After ¹⁴C-metalaxyl was applied to soil by drenching, 80.5% of the radioactivity taken up by the plant in 7 days accumulated in the cotyledons, 15.1% in the other aerial portions, and 4.4% in the roots.