Foliar Applications of Potassium Silicate Reduce Severity of Powdery Mildew on Cucumber, Muskmelon, and Zucchini Squash

Abstract

<jats:p>The effect of soluble potassium silicate applied to cucumber <jats:italic>(Cucumis sativus</jats:italic> L.), muskmelon <jats:italic>(C. melo</jats:italic> L.), and zucchini squash <jats:italic>(Cucurbita</jats:italic> pepo L.) on the severity of powdery mildew was examined. Application methods included amending nutrient solutions to a concentration of 1.7 m<jats:sc>m</jats:sc> Si and foliar sprays containing 1.7, 8.5, 17, and 34 m<jats:sc>m</jats:sc> Si. Untreated plants and plants sprayed with distilled water were used as controls. The leaves of all plants were inoculated with known concentrations of conidia of <jats:italic>Sphaerotheca fuliginea</jats:italic> (Schlecht.:Fr.) Poll. (cucumber and mu&amp;melon) or <jats:italic>Erysiphe cichoracearum</jats:italic> DC.: Merat (zucchini squash) 1 day after the sprays were applied. Inoculated leaves on plants receiving the Si-amended nutrient solution or foliar sprays of ≥ 17.0 m<jats:sc>m</jats:sc> Si developed fewer powdery mildew colonies than those on control plants. Results of a separate experiment that included a potassium spray, indicated that the active ingredient of the potassium silicate sprays appears to be Si. Experiments to test the persistence of Si foliar sprays on cucumber demonstrated that a 17 m<jats:sc>m</jats:sc> Si spray applied 7 days before inoculation with <jats:italic>S. fuliginea</jats:italic> reduced mildew colony formation.</jats:p>

Particle films and their applications in horticultural crops

“…In this method, a hydrophobic layer of particles keep water physically separated from the plant surface which helps in suppressing several diseases such as powdery mildew, sooty blotch, fly speck, and fire blight Mendgen et al, 1992;Menzies et al, 1992). The particulate material did not interfere with the action of conventional bactericides, fungicides or pH modifying agents.…”

“…Potassium silica application was effective in reducing powdery mildew in apple Menzies et al, 1992). White wash was useful in suppressing the transmission of citrus stubborn disease (Gumpf et al, 1981) and papaya decline (Franck and Bar-Joseph, 1992).…”

Effect of root and foliar applications of soluble silicon on powdery mildew control and growth of wheat plants

“…However, there is no strong evidence that Si can be absorbed by leaves and few scientific studies have confirmed the benefits of Si amendments through foliar applications. Some positive effects have been reported on cucumber, muskmelon, zucchini and grape to control powdery mildews Menzies et al 1992). Nevertheless, for those studies, Si concentrations of 17 mM in the form of potassium silicate were reportedly used which far exceeds the standard 1.7 mM in root applications.…”

Management of Anthracnose in Common Bean by Foliar Sprays of Potassium Silicate, Sodium Molybdate, and Fungicide

“…Among the defense mechanisms enhanced by Si is the formation of a physical barrier below the cuticle after monosilicic acid polymerization as well as an increase in the concentrations of total soluble phenolics and phytoalexins and higher activity of defense enzymes (18,33). In dicotyledonous plants such as cucumber, melon, and pumpkin, foliar applications of potassium silicate (KSi) reduced the number of colonies of Sphaerotheca fuliginea (23). On bean, foliar application of sodium silicate decreased the area under anthracnose progress curve by 62% (25).…”