The Effects of Plant Extracts of Reynoutria sachalinensis on Powdery Mildew Development and Leaf Physiology of Long English Cucumber. F. Daayf, Biocontrol Laboratory, Centre de Recherche en Horticulture, Departement de Phytologie, Universite Laval, Quebec, Canada, G1K 7P4 . A. Schmitt, Federal Biological Research Centre for Agriculture and Forestry, Institute for Biological Control, HeinrichstraBe 234, 64287 Darmstadt, Germany; and R. R. Belanger, Biocontrol Laboratory, Centre de Recherche en Horticulture, Departement de Phytologie, Universite Laval, Quebec, Canada, G1K7P4. Plant Dis. 79:577-580. Accepted for publication 23 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0577.

An aqueous formulation of concentrated extracts (Milsana flussig) from leaves of the giant knotweed, Reynoutria sachalinensis, applied weekly at a concentration of 2%, provided control of powdery mildew (Sphaerotheca fuliginea ) on long English cucumber that was as effective as benomyl. In two separate experiments, this treatment significantly reduced the severity of powdery mildew compared to control plants. Fruit yield was not affected by the treatment, even though repeated applications of Milsana induced a greener and glossier coloration of the leaves, which became brittle to the touch. A rapid and distinct accumulation of fungitoxic phenolic compounds occurred in leaves treated with Milsana, especially in infected leaves. A slight inhibition of conidia! germination was the only direct effect of Milsana on S. fuliginea. These results support the hypothesis that Milsana may act indirectly by inducing plant defense reactions and that it may be useful in the integrated management of cucumber powdery mildew

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