To get rid of mold, change three growth requirements

[Guest guest]

Updated 6:13 AM on Friday, August 19, 2005

To get rid of mold, change three growth requirements

Wendell Horne

Eagle Columnist

http://www.theeagle.com/stories/081905/gardening_20050819006.php

The unsightly mold on roofs, siding and other building surfaces can

cause long-term structural damage. It's usually black in color and

fungal in nature. Generally, it grows in areas of poor air

circulation and in heavy shade. Green algae may develop in the same

places under the same conditions.

Three factors enable mold and algae growth: The organism must be

present, food must be available and favorable environmental

conditions - moisture and moderate temperatures - must exist. To

control growth, you must alter those three requirements.

•First, remove the fungus. A chlorine-based solution can do the job

in a matter of minutes. Use a chlorine laundry bleach such as Clorox

at the rate of 3/4 cup in 1 gallon of water.

If you spray the moldy surface with a chlorine solution, use a hose-

on sprayer that shoots a single stream of water 20 feet or more.

Initially, you should use the sprayer without bleach to wet the

target surface and plants in the area; the water buffers plants

against chlorine damage. Then add the appropriate amount of chlorine

bleach to the unit container. To produce about 8 gallons of spray

using a typical hose-on sprayer container, add 6 cups of bleach and

2 cups of water to the container; this gets as close as possible to

the correct mixing ratio.

Avoid the spray drift as you apply the bleach solution. When the

container is empty, you will have sprayed about 8 gallons of diluted

material on the surface.

In about five minutes, the stained surface should return to its

original color. The chlorine will evaporate quickly.

To protect plants, use water to wash down any nearby plant surfaces

that may have been hit with the bleach mixture. Do this promptly and

thoroughly.

Power-washing machines that deliver water under high pressure will

remove mold and algae, too. Unfortunately, they may erode or remove

paint.

Choose either the chemical or mechanical (power-washing) approach to

remove the unwanted growth from building surfaces. Then carry out

the procedure as recommended.

•Second, address the food supply to prevent the return of the fungus

or algae. The food source may be wood, paint, insect deposits or

dirt. If the fungus is growing on unpainted wood, paint it with a

product containing a mold inhibitor (sometimes referred to as a

mildewcide).

If the mold is growing on a painted surface, it may be feeding on

the paint itself. Again, repainting with a product containing a mold

inhibitor may be the answer.

If honeydew - a substance produced by insects - is the food source,

remove the plant or plants on which the insects are feeding or apply

a systemic insecticide around the plant's base.

•Finally, environmental factors usually can be changed by pruning

trees and shrubs that are interfering with air movement. Selectively

prune to maintain the natural shape of trees and shrubs.

Also make sure that water is not being trapped and held by an

improperly installed or maintained gutter system.

Moisture management is a major criterion in eliminating mold and

algae.

•Wendell Horne is a retired Texas A & M University plant pathologist

and consultant. His e-mail address is tallman@ txcyber.com.