Fungicides are a type of pesticide that preventatively and/or curatively control diseases that can harm—and sometimes kill—turfgrass and ornamentals. These products help professionals keep sports fields, golf courses, landscapes, and lawns free of harmful fungi. Whether you’re well-seasoned or are new to the green industry, understanding fungicides will help you use them effectively on the properties you treat.
How Fungicides Work
Contact fungicides form a protective barrier on the surface of the turf or ornamental plants. This barrier prevents spores from forming. Contact fungicides can work preventatively and curatively, depending on the target pathogen.
Systemic fungicides have the ability to become mobile in the plant once they’re absorbed. Some may be absorbed by the roots once in the soil or absorbed through the leaves and crown of the plant. They can be very mobile or only move locally from the absorption point. These products may offer protection down into the root zone and come as both preventatives and curatives.
Preventative vs. Curative
Preventative fungicides keep diseases from infecting turfgrass and ornamentals. They should be applied before disease symptoms appear and environmental conditions are favorable for disease.
Curative fungicides target diseases that have already infected turfgrass or ornamentals, halting the disease’s progression. They should be applied as soon as symptoms appear.
Common Fungal Diseases in Turfgrass
There are many different diseases that can damage the turfgrass you maintain. Here’s a brief overview of three common diseases.
Dollar Spot
Dollar spot causes small, tan lesions to appear on individual blades of grass, which then grow into circular patches ranging from one to three inches in diameter—around the size of a U.S. silver dollar. These infected areas may die if they aren’t treated promptly. Dollar spot thrives in hot and humid conditions, and its spores are easily spread by water, wind, and traffic. For chemical control, consider applying a broad-spectrum fungicide like Pillar SC or Lexicon.
Pythium Root Rot
Pythium root rot (PRR) is caused by water mold pathogens and primarily affects cool-season grasses. The pathogens thrive in wet conditions, making turf drenched by long periods of rainfall a prime candidate for the disease. Roots infected with PRR will have an unpleasant odor, appear brown, and be soaked with water. On the surface, turf may exhibit dead patches, thinning, and/or yellowing along the surface in streaks. Proper watering and drainage will help prevent PRR, but a preventative fungicide like CYA 345, Serata, and Insignia SC should be used as well.
Snow Mold (Pink and Gray)
Snow mold causes light-colored, circular patches to appear on turfgrass. Gray snow mold primarily attacks grass blades, while pink snow mold affects crowns and roots. While pink snow mold can develop at any time of the year when conditions are cool and damp, gray snow mold needs extended snow cover to develop. Use a dual-action fungicide with both contact and systemic qualities to combat snow mold. Some common, effective active ingredients include PCNB, chlorothalonil, fluazinam, propiconazole, and iprodione.
Common Fungal Diseases on Ornamentals
Powdery mildew and black spot are two common diseases that harm ornamental plants.
Powdery Mildew
Powdery mildew causes a thin, white coating of fungus to appear on the upper surfaces of leaves. This disease thrives in cool, humid conditions and is spread by wind and rain. In addition to its unsightly appearance, powdery mildew causes leaves to yellow and drop prematurely. Pruning ornamentals can help increase air circulation and help prevent powdery mildew from appearing. A curative, systemic fungicide like Tourney EZ, which contains metconazole, can eliminate the disease once it appears.
Black Spot
Black spot is a disease that causes black (and sometimes purple) spots to appear on the upper sides of rose leaves and can spread to stems and canes. As the disease progresses, yellow rings develop around the spots and the leaves fall off. While black spot will not kill rose plants, it will weaken them. Black spot thrives when air temperatures are cool and moisture is high. It spreads via water, wind, and insects. To stop the spread of black spot, infected leaves will need to be pruned and disposed of. For black spot control, consider Eagle 20EW, a systemic fungicide. This fungicide works both preventatively and curatively to control black spot.
Important Considerations for Fungicide Applications
- Cultural practices like proper mowing or pruning, irrigation, and fertilization can reduce disease pressure
- Follow label instructions to protect people, animals, and the environment.
- Rotate products from different FRAC (Fungicide Resistance Action Committee) groups to prevent resistance.
- Ensure application equipment is correctly calibrated to deliver uniform coverage at the correct rate.
For more information and personalized product recommendations, reach out to your ATS rep. If you’re new to ATS, find a rep near you.
