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Translocation of Metalaxyl and RE26745 in Potato and Comparison of Foliar and Soil Application for Control of Phytophthora infestans. Randall C. Rowe, Associate Professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster 44691 and Ohio State University, Columbus 43210. Plant Dis. 66:989-993. Accepted for publication 13 February 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-989.

The efficacy of metalaxyl and RE26745, systemic fungicides specific for fungi in the Peronosporales, was tested with an excised-leaf bioassay technique for control of Phytophthora infestans on potatoes grown under greenhouse conditions and in the field. In greenhouse tests, P. infestans was controlled up to 90 days with soil application of either material. Both were translocated from lower to upper foliage, but only RE26745 showed appreciable basipetal movement. In-furrow field treatments with both materials provided control up to 60 days after planting, but only the higher rates of RE26745 were effective up to 90 days. RE26745 provided control longer than metalaxyl when applied as a foliar spray at flowering. In field tests, using an in-furrow application followed by one or two foliar sprays, RE26745 provided season-long control but metalaxyl was less effective.

Keyword(s): chemical control, potato late blight.