How Does Daconil Fungicide Work?

Daconil fungicide kills fungi by reducing molecules of the antioxidant glutathione inside fungal cells to unreactive forms that do not participate in essential biochemical reactions, which leads to the death of the fungal cells. Daconil's active ingredient is chlorothalonil, which is an organic, broad-spectrum fungicide that controls mold, mildew, bacteria and algae. It is also used as a pesticide, acaricide and wood protectant.

Daconil concentrate prevents and controls more than 80 diseases in flowers, crops, shrubs, fruit and trees. Gardeners mix a small amount of the concentrate with water and spray the solution onto plants to control plant diseases such as blight, rust, leaf spots, fruit rot and anthracnose. The product is for outdoor residential use only and is safe to use on edibles. A 16-ounce bottle can make 64 gallons of solution. Customers on The Home Depot rate the product 4.4 out of five stars, based on 19 reviews.

Chlorothalonil was first registered for use in the United States in 1966 and has become the third most popular fungicide in the country. The U.S. Environmental Protection Agency estimates that combined agricultural and non-agricultural applications used about 15 million pounds of the fungicide each year from 1990 to 1996. The biggest agricultural applications were for use in peanuts, potatoes and tomatoes.

The U.S. EPA classifies chlorothalonil as an eye and skin irritant and possible carcinogen. Scientists blame its widespread use as a factor in the decline of the honey bee population. It is highly toxic to fish and aquatic invertebrates.