There are numerous fungal diseases out there that can plague your customers’ lawns and ornamental plants and there are several different ways to go about controlling the unsightly infestations.
When dealing with fungal diseases, remember the old adage that “the best defense is a good offense.” By taking preventive action, you can decrease the chances of infection.
“We do in-house tissue testing weekly to see what the likelihood of a disease attack is,” says Todd Woodfield, manager at Abby Farms. “Based off the data we get from these five tests, either we treat or don’t treat the plant.”
Woodfield explains that plants can become susceptible to disease if there is a nutrient that is locked up and unavailable to the plant, undermining its overall health.
“Prevention is simple,” he says. “Don’t overwater and spacing is critical so we have air movement between plants, and don’t overdo it with fertilizers.
“If you’re going to use fertilizer,” Woodfield says, “research it. Many fertilizers will induce problems by killing the beneficial bacteria or fungi in the soil. Protect you soil life at all costs.”
Know the weather
Sometimes, even when the proper precautions have been taken, the weather will create favorable conditions for fungal diseases.
“We generally say the wetter the better for disease development,” says Derek Settle, Ph.D., a technical specialist with the Bayer Green Solutions Team. “A pathogen is basically a type of mold that has specialized as a plant parasite. As a general rule of thumb, foliar diseases need about 10 hours of wetness.”
As for the most challenging season for infections, experts say it depends on the specific fungal disease and the region.
“It really depends on where you are in the country,” says Nancy Rechcigl, a technical field manager for Syngenta. “Rust diseases show up in the spring and fall in the South, but up north it’s the spring and summer.”
The two most common fungal diseases that are causing trouble right now are large patch, found in warm-season grasses, and leaf spot among ornamentals.
“Some of these diseases occur following stress,” Settle says. “(If you) had a very hot, stressful summer that was overly dry and then wet. In the fall, you would expect stress-related plant pathogens like leaf spots.”
Cool-season turf and plants are more susceptible to fungal diseases during the summer, when they are already strained, while warm-season grasses are more likely to face problems during the cooler months.
When offering fungicide applications, take the time to educate your clients on the benefits of having preventive sprayings rather than sprayings to treat a problem.
“The best way to use a fungicide is to use it as a preventative,” says Dan Loughner, a field scientist with Corteva Agriscience. “You don’t want to use it as a curative if it can be helped, but most homeowners are going to call when they see the disease, not before.”
When choosing a fungicide, it is better to choose a broad spectrum product. That way you can use it to treat all your different properties and have most of the common fungal diseases under control.
However, note that oomycetes, such as Pythium and Phytophthora, typically need products that have specific activity against these pathogens, according to Rechcigl.
It is important to be aware of what plants are prone to certain diseases so you can treat them proactively.
“Crape myrtles get powdery mildew, roses get rust and powdery mildew,” Rechcigl says. “Proactive spraying can prevent them from happening.”
When you are preparing your spraying program, make sure to cycle in different modes of action. Even though tolerance build up isn’t common in the landscaping field, it is still best to follow the fungicide label and rotate the types.
“You want to alternate fungicides every couple of cycles,” Loughner says. “You wouldn’t want to make multiple applications of the same mode of action without changing to a different type.”
What products to use
Whether your fungicide service is a preventive program or a curative response will determine the choice of a liquid or granular product.
Liquid formulation is preferred due to the good foliage coverage and it can immediately act against the issue, making it the obvious choice when treating fungal diseases that have already taken hold.
There are some situations where sprays can’t be used and a granular version can take its place. Granular fungicides also work well in preventive programs because they’re able to get ahead of the disease and are taken up through the plant over time.
For those looking for the best of both worlds in Bayer’s products, Armada 50 WG features triadimefon and trifloxystrobin, the active ingredients of Bayleton FLO and Compass 50 WG, respectively.
“By having two modes of action, Armada helps to mitigate fungicide resistance development,” Settle says.
When handling just ornamental fungal diseases, broad-spectrum fungicide Mural from Syngenta is says to be very effective against powdery mildew and anthracnose thanks to its two active ingredients, Solatenol and azoxystrobin.
Syngenta also has Banner Maxx II, which is a systemic fungicide that can control both turf and ornamental fungal problems.
Corteva Agriscience’s Eagle 20EW can be used on ornamentals, fruit trees and a majority of turf varieties and is says to have a longer residual effect. Dithane can be used as a protectant for foliage from diseases such as rust and scab.
Identify the culprit
However, knowing what products are available isn’t going to solve the problem if the disease has been incorrectly identified.
“First, you have to get the correct identification, and most people are not well equipped to do that,” Settle says. “Take a sample of the plant with a disease symptom to a state extension office or university diagnostic lab and have it examined. The second point is that with some of these diseases, you can get the fungicide to stop it – but you need to ask why is this happening? Is it the weather or the growing site? Look at the cultural practices to ensure that the environmental conditions are good and providing enough light and air, which are just as important as fungicide solutions.”