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Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved
Home Garden Fungicides for Disease Control
Controlling plant diseases is often a confusing and difficult task. The recommendation to spray a fungicide often adds to the confusion because many registered fungicides are not readily available to home gardeners.
Several companies cater to the backyard grower. In Utah, these companies include Ortho, Lily Miller, Green Light, HiYield, Fertilome and Spectricide, Monterey and Cooke.
Fungicide names are confusing. Plant pathologists usually use the general or common name such as chlorothalonil. Manufacturers and retailers use trade names. For example, chlorothalonil is packaged as Daconil or Ortho Multi-Purpose Fungicide for the home market and as Bravo for commercial markets.
There are differences in the formulation (such as a liquid or powder); for ingredient and in how it is used (as a spray or drench, for example). Some products have more than one type of chemical together. The ingredient list on the label will tell you what is in the product.
Triadimefon (Bayleton) An excellent curative and preventive fungus control for lawns but only available as granules.
Captan – An excellent general-purpose fungicide that controls many plant diseases. It is not effective on powdery mildews and rusts. Use it as a spray, dust, dip, or seed treatment. Captan is labeled for ornamentals, lawns, vegetables, and fruit but only when mixed with other pesticides. It controls leaf spots, blights, and fruit and vegetable rots.
Chlorothalonil (Daconil, Ortho Multi-Purpose Fungicide) - Another good, general-purpose fungicide for foliar fungal diseases as it breaks down rapidly in soil. It lasts well and is labeled for vegetables, fruits, and many ornamentals including shade trees. Allergic people may develop skin rashes.
Copper based compounds (Bordeaux mixture, Microcop) - There are many copper products, but copper sulfate is the most common. Bordeaux mixture, made by adding copper sulfate and calcium hydroxide to water, was the first fungicide and was used extensively in France to control downy mildew on grapes.
It is a highly effective because it stays on the plant surface even after rain. It is often used as a dormant spray since it may burns tender plant tissues. Copper controls many fungal and bacterial diseases including cankers, galls, blights, and leaf spots. It is not effective against powdery mildews. It is widely recommended because it has no tolerance levels because it has low toxicity and insolubility in water.
Horticultural Oils (Neem Oils such as Rose Defense, Sunspray Ultra-Fine Year-Round Pesticidal Oil) – These include petroleum oils and plant oils. These are effective if powdery mildew is severe and they will eradicate the fungi if you thoroughly cover the plant surfaces. Do not use when plants are wet from rain, irrigation or dew.
Mancozeb (Green Light Broad Spectrum Mannose Fungicide) – A difficult fungicide to find in the stores but is effective on many fungal diseases. Registered for use on lawns, fruits, vegetables and ornamentals.
Myclobutanil (Immunox, Spectricide) - One of the most effective fungicides available to homeowners particularly against powdery mildew. It is also effective against rusts and many leaf spots. Apply to the plant foliage and rotate with other fungicides to prevent pest resistance.
PCNB (Hi-Yield Turf and Ornamental Fungicide) – Primarily for snow mold on turf and for bulbs.
Soaps (Safer's Insecticidal Soap) – Soaps help control powdery mildew and soft bodied insects. Thorough coverage of the plant surfaces is essential.
Sodium or Potassium Bicarbonates (Remedy) - Sodium bicarbonate is baking soda and potassium bicarbonates are used to prevent salt build up from the sodium form. Not as effective as other fungicides but better than nothing. Usually used with oils, which increase their effectiveness.
Sulfur (many formulations containing the word sulfur.) - Elemental sulfur is active against powdery mildews, some rusts, leaf blights, and fruit rots and is labeled for fruits, beans, and many ornamentals. Disadvantages are a short effective control time and specific temperature restrictions.
Sulfur is active as a vapor at higher temperatures but when the temperature is over 85 °F, some foliar burn is likely. At low temperatures, there is no fungicidal activity. 'Concord' grapes or apricots are sulfur sensitive and will burn at any temperature. Often leaves and objectionable residue on the plants and is caustic to skin.
Tebuconazole (Bayer Advanced Garden Disease Control for Roses, Flowers & Shrubs) cures, stops and prevents plant diseases. It is systemic and provides rainproof protection against most common plant diseases such as black spot, powdery mildew, rust and other diseases.
Thiophanate methyl (Green Light Systemic Fungicide, Halt) - A close relative to benomyl (Benlate) It is registered on ornamentals, lawns and some fruit trees.
Triforine (Funginex) - A locally systemic fungicide that controls powdery mildew, rusts, and some leaf spots or blights. It is labeled for use on several ornamental plants and is used to control important rose diseases.
The label is the legal document. No matter what anyone else says, always follow label directions. To do otherwise is against the law.