Evaluation of Silicon for Managing Powdery Mildew on Gerbera Daisy

ABSTRACT

Powdery mildew, caused by Erysiphe cichoracearum or Podosphaera fusca, is a common disease of gerbera daisy (Gerbera jamesonii) grown in Florida. Previous studies demonstrated that silicon reduces powdery mildew in Arabidopsis, cucumber, grape, strawberry, and wheat. In this study, two silicon (Si) sources, calcium silicate and potassium silicate, were evaluated for their ability to reduce powdery mildew in gerbera ‘Snow White’. The effect of calcium silicate in flower quality and the silicon uptake was also determined. Calcium silicate was not effective in reducing powdery mildew or in improving flower quality. The silicon content of gerberas treated with potassium silicate was slightly greater than that in plants treated with calcium silicate. However, the severity of powdery mildew was not reduced by potassium silicate. The results suggest that silicon may not be useful for managing this disease of gerbera daisy, possibly due to the low accumulation of silicon by gerbera leaves.

Keywords:

• potassium silicate
• calcium silicate
• gerbera daisy
• powdery mildew

Notes

^zDisease severity rated on a 0 to 5 scale, where 0 = no powdery mildew symptoms and 5 = 81 to 100% of upper leaf surface covered with powdery mildew symptoms.

^yAUDPC = area under the disease progress curve.

^xPr > F: significance level of F value by linear regression analysis.

^xPr > F: significance level of F value by linear regression analysis.

^xExperiment 1 conducted from 16 August to 26 September 2006.

 ^yExperiment 2 conducted from 18 January to 16 February 2007.

 ^zSignificantly different.

^yExperiment 1 conducted from 16 August to 26 September 2006.

 ^zExperiment 2 conducted from 18 January to 16 February 2007.

^zMeans in columns and within experiment followed by different letters are significantly different according to the Waller-Duncan k ratio t test (P ≤ 0.05).

 ^yExperiment 1 conducted from 16 August to 26 September 2006.

 ^xExperiment 2 conducted from 18 January to 16 February 2007.