Neuveni, M., Golan Research Institute, University of Haifa, P.O. Box 97, Qasrine 12900, Israel
Agapov, V., Golan Research Institute, University of Haifa, P.O. Box 97, Qasrine 12900, Israel
Reuveni, R., Agricultural Research Organization, Division of Plant Pathology, Newe Ya'ar Research Center, P.O. Box 90000, Haifa 31900, Israel

Powdery mildew in greenhouse-grown cucumber (Cucumis sativus L.), caused by Sphaerotheca fuliginea (Schlecht.:Fr.) Pollacci, was significantly controlled by a foliar spray pre-inoculation treatment of 20 mM aqueous solutions of either monopotassium phosphate or potassium nitrate, or a 0.01% solution of the systemic fungicide pyrifenox. Further foliar sprays of mono- or dipotassium phosphate, sodium bicarbonate (1%) and pyrifenox remarkably suppressed powdery mildew colonies on diseased foliage. Solutions of 25 mM of mono- or dipotassium phosphates and potassium nitrate applied on a 7 or 14 day schedule were highly protective against natural infection by the mildew fungus in the greenhouse. Pyrifenox was not significantly more effective in controlling S. fuliginea than either phosphate or the potassium salts. These salt solutions were not phytotoxic to plant foliage. The inhibitory effectiveness of phosphate and potassium salts makes them useful biocompatible fungicides and possibly ideal foliar fertilizers for disease control in the greenhouse. Copyright © 1996 Elsevier Science Ltd All rights reserved.