Translocation of Metalaxyl and RE26745 in Potato and Comparison of Foliar and Soil Application for Control ofPhytophthora infestans

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Abstract
The efficacy of metalaxyl and RE26745, systemic fungicides specific for fungi in the Peronosporales, was tested with an excised-leaf bioassay technique fore control of P. infestans on potatoes grown under greeenhouse ocnditions 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 1 or 2 foliar sprays, RE26745 provided season-long control but metalaxyl was less effective.