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How you can get a leg up on brown and large patch

June 8, 2022 -  By
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Experts suggest two fungicide applications in the fall, four weeks apart, to treat large patch. (Photo: FMC)

Experts suggest two fungicide applications in the fall, four weeks apart, to treat large patch. (Photo: FMC)

Although the same pathogen Rhizoctonia solani causes brown and large patch, the similarities of the diseases end there. After all, the pathogens affect different types of turfgrasses at different times of the year. For instance, brown patch infects cool-season turfgrass during the summer, while large patch develops on warm-season turfgrass in the fall, particularly once soil temperatures fall below 70 degrees F.

Tina Bond, Ph.D., technical service manager with FMC Global Specialty Solutions; Zac Reicher, Ph.D., green solutions team specialist for Bayer and Ian Rodriguez, Ph.D., Quali-Pro technical services manager, share the tools pros should consider to get a leg up on brown and summer patch.

Prevent through cultural controls

Experts recommend professionals follow appropriate agronomic practices, such as proper irrigation timing, correct mowing heights and adequate fertility. Bond also advises professionals to adjust irrigation cycles to run early in the morning rather than late afternoon or early evening to reduce turfgrass wetness. Enhancing drainage and decreasing thatch will also reduce infection.

Moisture plays a role in many turf diseases, including brown patch. Experts suggest pros deploy any method that reduces the duration of leaf wetness. (Photo: Control Solutions Inc.)

Moisture plays a role in many turf diseases, including brown patch. Experts suggest pros deploy any method that reduces the duration of leaf wetness. (Photo: Control Solutions Inc.)

If an area has a history of disease pressure and underlying moisture issues are simply out of professionals’ control, they should consider preventive fungicide applications. Bond says, “They’re very important in managing patch diseases, prior to development.”

“For brown patch control, applications should be made when nighttime temperatures first appear consistently above 65 degrees Fahrenheit under high relative humidity with daytime temperatures consistently above 80 degrees Fahrenheit,” Bond says of FMC’s fungicides. “For large patch, applications should begin in the fall when soil temperatures drop below 70 degrees Fahrenheit.”

As temperatures rise, the window of disease activity for brown and large patch tends to expand, says Reicher. Longer periods of conducive disease conditions will require additional fungicide applications and increased application rates.

“Consequently, it’s increasingly important to enhance cultural condition — while also maximizing airflow and soil drainage and pruning trees to reduce shade — to favor turfgrass growth and discourage diseases,” he says.
Experts also say moisture plays a role in many turf diseases. As a result, any method that helps reduce leaf wetness duration will help prevent either disease. In addition, turf management professionals should avoid soluble nitrogen during periods of high disease pressure.

“Managing moisture goes a long way on these diseases,” says Rodriguez. “If an underlying irrigation program or drainage issue isn’t addressed, disease symptoms will likely reappear three to four weeks after a fungicide application.”

Fungicide controls

Bond recommends fluoxastrobin fungicides, as these products offer long-lasting brown and large patch control. LCOs can achieve efficient brown patch control while utilizing 28-day application intervals in higher cut turf, she says. Additionally, Rodriguez suggests utilizing strobilurin fungicides, such as azoxystrobin.

Experts say pros should apply fungicides — especially strobilurin fungicides such as trifloxystrobin and DMI fungicides such as triadimefon — every four to six weeks.

Meanwhile, LCOs should use these fungicides for large patch in lawns with regular outbreaks. Reicher recommends lawn care professionals use two fall applications, starting when the five-day average of 2-inch soil temperatures ranges between 72 and 75 degrees F, followed by a second application four weeks later.

“There are limited fungicides available for residential lawns, but DMI fungicides are still the most effective mode of action for large patch,” Reicher says. “Complete control of large patch is difficult in especially problematic lawns, so an additional spring application at 50 percent green-up may be needed to increase control.”

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