Vegetable Garden Fungicides

Squash plants in a vegetable garden.

Fungicides are an important tool for disease control in any vegetable garden. Many diseases are actually fungal in origin and these chemicals can safely and effectively prevent and control these pathogens. Both man-made and organic fungicides are widely available in several forms. Sprays, powders and systemic treatments exist and can be found at your local garden center.

Diseases Prevented by Fungicides

Most fungicides are preventative in nature. Once a plant is infected, most of these chemicals will not help much. Treat the plants early and as often as indicated by the instructions for the product; most suggest once a month. If a plant is infected, remove infected leaves and parts and treat with fungicide to prevent the spread of further infection. Some diseases prevented by fungicides include downy mildew, various blights, Alternaria, rust, botrytis, bitter rot, scab and black scab, among many others. Not all fungicides will control everything; check labels for a list of what each product controls.

Using Fungicides

Most fungicides come in spray form, but some come as a dust that is sprinkled on the plants. Many are safe to use on most crops but some are not indicated on certain types of plants. Check the label of any fungicide you intend to buy for a list of approved usages. Spray types should be applied simply to the foliage of the plant. Systemic fungicides are either applied to the ground around the plant or mixed with water and applied around the plant; these types are actually absorbed by the plant and act like a vaccine. All fungicides are toxic and should be handled with care; gloves are recommended and avoid breathing in sprays, fumes or dust.

Some Common Fungicides

Several man-made chemicals are used as fungicides in garden products, including chlorothalanil, Captan, Mancozeb and Maneb. Some systemic fungicides include benamyl, triforine, triadimefon and thiophanate-methyl. Triforine is used in Funginex brand, thiophanate-methyl in Green Light Systemic Fungicide brand and the others are found in several products.

Organic Fungicides

Organic gardeners also have several options to choose from when looking for an effective fungicide. Bordeaux mixture, lime-sulfur, fungicides containing copper and others containing sulfur are all considered organic. Many brands use these compounds, including Bonide, Safer and others. Most will clearly be labeled as organic.

What Fungicides to Use on Specific Crops

Many fungicides are indicated for use on certain crops and not on others; each brand will clearly list the vegetables that it is safe to use on. However, several online resources are available to determine the fungicide most appropriate for your specific need; see the Resource section for links to these lists.

References

• University of Minnesota: General Fungicide Information
• North Dakota State University: General Fungicide Information

Resources

• North Dakota State University: Plant Disease Management in the Home Garden
• University of Georgia: Homeowner Fungicide Guide
• Missisippi State University: List of Fungicides and Uses