THE EFFECTS OF PLANT-EXTRACTS OF REYNOUTRIA-SACHALINENSIS ON POWDERY MILDEW DEVELOPMENT AND LEAF PHYSIOLOGY OF LONG ENGLISH CUCUMBER

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 (Sphaerorheca 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 conidial 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.