Cobweb mold is a fungal growth that appears on plants, mushrooms and even on bare areas of soil. It is characterized by a white or gray, fuzzy appearance on the surface of the soil or plant that very much resembles a cobweb. It is caused by contaminated soil or compost and thrives in high levels of humidity combined with high temperatures. Cobweb mold infestations are serious since the spores reproduce rapidly and will kill plants if not stopped.
Place the affected plant in a location where the temperature is lower than 65 degrees Fahrenheit. Cobweb mold thrives in high temperatures and dies when temperatures drop lower than 65 degrees. Place a thermometer in the area to measure the temperature accurately.
Lower the relative humidity level of the area until it is below 92 percent. Place the affected plant in an indoor location, if it's not already, and turn on a dehumidifier. Allow the plant to sit in the location with the dehumidifier running until the cobweb mold disappears. Do not turn the humidity down lower than 92 percent as it will negatively affect the plant. A hygrometer placed in the location will indicate the relative humidity level.
Increase the air circulation in the area where the cobweb mold is growing. If the mold is contained in a jar or plastic container, remove the lid and stop watering until the mold dies off. Turn on ceiling fans and open doors and windows in the area to let more air circulation in.
Apply a fungicide to the surface of non-edible, outdoor plants that are infected with cobweb mold. Spray the mold, as well as the plant stem and leaves with the fungicidal solution until they are saturated. Fungicides are not always effective at killing cobweb mold, but they will help to diminish it on outdoor plants where temperature and humidity cannot be easily controlled.