M. Reuveni et al., CONTROLLING POWDERY MILDEW CAUSED BY SPHAEROTHECA-FULIGINEA IN CUCUMBER BY FOLIAR SPRAYS OF PHOSPHATE AND POTASSIUM-SALTS, Crop protection, 15(1), 1996, pp. 49-53
Powdery mildew in greenhouse-grown cucumber (Cucumis sativus L.), caus
ed by Sphaerotheca fuliginea (Schlecht.:Fr.) Pollacci, was significant
ly controlled by a foliar spray pre-inoculation treatment of 20 mM aqu
eous solutions of either monopotassium phosphate or potassium nitrate,
or a 0.01% solution of the systemic fungicide pyrifenox. Further foli
ar sprays of mono- or dipotassium phosphate, sodium bicarbonate (1%) a
nd pyrifenox remarkably suppressed powdery mildew colonies on diseased
foliage. Solutions of 25 mM of mono- or dipotassium phosphates and po
tassium nitrate applied on a 7 or 14 day schedule were highly protecti
ve against natural infection by the mildew fungus in the greenhouse. P
yrifenox was not significantly more effective in controlling S. fuligi
nea 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 fungici
des and possibly ideal foliar fertilizers for disease control in the g
reenhouse.