Hydrogen peroxide, a multipurpose solution most commonly known for cleaning wounds, also works as a fungicide on plants. Peroxide works both as a preventative measure against fungus and as a treatment for fungus already on the plant. Use peroxide spray twice a week in humid locations or once a week in arid weather. Avoid spraying plants that have damaged leaves or that recently have been transplanted.

1、Fill a spray bottle with 3-percent hydrogen peroxide -- the kind easily found at supermarkets and pharmacies.
2、Spray one leaf of the houseplant with the solution. Wait one day to see if the leaf reacts negatively to the hydrogen peroxide. Few plants have a problem with the spray.
3、Spray the tops and bottoms of the plant leaves with the solution to prevent or treat fungus.

From Network Resources