Control of powdery mildew (Leveillula taurica) on tomato by foliar sprays of liquid potassium silicate (K2SiO3)

A foliar application of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of tomato for 2 years in the field conditions on susceptible cultivar Alida F1. Powdery mildew in field-grown staked tomato, caused by Leveillula taurica was significantly controlled by a foliar spray of either K2SiO3 or Bayleton + sulfur. Potassium silicate applied on a 12 day schedule was highly protective against natural infection by the mildew fungus in the field conditions. The disease severity indexes (DSI) were 77.5 and 74.7% in control plots in 2006 and 2007, respectively, and were significantly different (P < 0.05) from those in the K2SiO3 plots with 5.8 and 4.6% in 2006 and 2007, respectively. Potassium silicate concentration (1 g/1 L water) used in the present study were not phytotoxic to plant foliage. The inhibitory effectiveness of potassium silicate makes it a useful biocompatible fungicide and possibly ideal foliar fertilizer for disease control in the field.Key words: Powdery mildew, potassium silicate, fungicide, tomato