When powdery mildew shows up on your plants, you need to act quickly to prevent it from taking over. If the infected plants are in an isolated indoor area like a greenhouse or a conservatory with a door, a sulfur burner is one option to clear up the infection quickly.
Powdery mildew is a fungal infection that attacks everything from flowering plants to grass. It starts out as a few white specks on the upper side of a plant's leaves. As the infection gets worse, the specks spread until the leaves and stem are coated in a flour-like layer of powdery mildew. The mildew can spread among plants of the same species. Spreading is especially likely in plants that are very close together with poor air circulation around their leaves.
Powdery mildew is unsightly. It ruins the appearance of any ornamental plants it infects. As the mildew problem gets worse, infected plants drop their leaves early. New leaves grow in small and misshapen. If the plant blooms, the flowers could be deformed. Powdery mildew is rarely serious enough to kill a plant, but it will prevent it from thriving and could weaken it enough so that it doesn't bear fruit.
Available for purchase at nurseries and garden supply stores, a sulfur burner is used to fight fungal infections in plants. It works best in enclosed areas like a greenhouse. Sulfur burners vaporize sulfur and blow the mist onto plants, coating them and the mildew. Sulfur kills mildew and prevents its spores from germinating, which prevents the infection from spreading. The first time you run a sulfur burner, turn it on overnight and let it run for 12 hours. Wait a few days, then run it again for about two hours. Run it again every few days for a couple of hours until the infection clears.
Do not be in the same room as the sulfur burner while it runs; breathing in concentrated vaporized sulfur can cause respiratory inflammation. For this reason, use the burner only in rooms that can be isolated by closing a door; this prevents children and pets from accidental exposure to the sulfur cloud produced by the burner. The sulfur will also coat walls and windows in addition to plants. If possible, leave it there until the powdery mildew is under control, then wipe away the sulfur residue with a damp sponge. If treatment with a sulfur burner hasn't cleared the infection in a few weeks, it is time to discard the infected plants and replace them with new ones.