Small name, big problem – golf course industry

by | Aug 21, 2021 | Golf Courses

If your lawn knowledge is about as shallow as a standard mug, you might think the term mini-ring sounds innocuous and almost cute. A mini ring could be some kind of decoration or an area reserved for special guests.

It’s none of those things, of course. No, mini-ring is a malignant and permanent fungal disease that seldom says as much as hello before digging deep into the warm season’s greenery, covering it with spots and bumps in autumn and winter through to early spring. You may know it by its darker name: leaf and vaginal rot.

Particularly prominent in the transition zone and especially in the whole of Florida, mini-rings most often attack Bermuda grass greens and, according to Dr. Emma Lookabaugh performing on other warm season grasses, including Paspalum, Millipede, and St. Augustine, is a technical specialist for BASF in Raleigh, North Carolina. Ultra-dwarf varieties of Bermuda grass and low-fertility turf are particularly susceptible.

“Early symptoms are bronze spots with a diameter of a few centimeters to over a foot,” says Lookabaugh, who has worked intensively with Dr. Bruce Martin, Professor Emeritus, Turfgrass Pathology, Clemson University. “It has been described as causing irregular frog-eye spots that have scalloped edges, that is, not perfect circles. There are no noticeable spots or lesions on the leaf blade as we can see in other Rhizoctonia diseases. Lower leaves can appear bleached or blotchy, and in extreme cases, blotches can cover entire areas of the green. It can be a pretty serious illness when the conditions are right. “

What makes the mini-ring so annoying to superintendents and researchers is that while they have determined the optimal temperature at which the pathogen will grow – 83 to 97 degrees Fahrenheit – the pathogen may not even be active by the time symptoms show up. Low fertility, extreme growth regulation and mechanical damage such as aeration and scarification can stress the lawn and trigger symptoms.

“All of this puts a strain on the turf,” says Lookabaugh, “especially if you use some of the more aggressive aeration practices and bring them into the season later, like in July. If lawns are already suffering from drought stress or low fertility, these practices can lead to more pronounced symptoms. “

The big question, Lookabaugh says, is how do superintendents and agronomy directors predict when mini-ring will appear on their greens? They need to be proactive, not curative, and they need a targeted fertility and irrigation plan.

“It’s definitely not easy,” she says. “The mini-ring, in particular, is a disease that can take superintendents by surprise because they don’t plan on it. It sneaks up on you because the pathogen is active in the summer long before you see the symptom expression. Courses with a history of mini-rings on their greens should definitely be more proactive and keep an eye on their preventive fungicide applications throughout the summer.

“Often times we don’t do many applications on lawns in the warm season in the middle of summer, rather on demand, but if you have mini-rings in the past you need a more rigorous fungicide program throughout the summer and you may need yours Shorten the spraying intervals. “

Working with research done by Martin, Lookabaugh recommends switching your nitrogen source to urea when mini-ring mushrooms are active as your nitrogen source. “Just changing your nitrogen sources can make a big difference,” she says. “Combining this with good preventative fungicides is the ideal program to deal with this disease.” Collecting soil samples and providing adequate and balanced fertility based on these soil sample results can also help reduce disease pressures.

And while the mini ring differs significantly from the fairy ring, application programs for the two diseases can work together. Lookabaugh and the rest of their team at BASF recommend a 14- to 21-day spray program to combat the mini-ring and, “If you are already on a preventive fairy ring program, you will likely benefit twice from these applications in your fungicide selection.” August applications can trigger preventive programs against root rot. “If you’re using a robust fungicide program, the mini-ring guard is likely already built in. You may just need to add a few extra applications to support your summer rotation. ”According to Lookabaugh, BASF recommends adding the Lexicon® Intrinsic® brand fungicide with the Maxtima® fungicide or the Navicon® Intrinsic brand fungicide with the Xzemplar® fungicide rotate to combat the mini ring.

Lookabaugh also recommends using soil wetting agents every two weeks, a practice that will help manage local dry spots and improve lawn quality under stressful conditions such as drought and high pedestrian traffic. Regular use of wetting agents can also augment existing fungicide use by helping to bring the fungicide deeper into the crown and root zone, where many soil-borne pathogens are most active.

“There’s a lot we don’t understand about this disease, from basic epidemiological questions to effective fungicide rotations,” Lookabaugh says. “We also need more research on the effects of not just other nitrogen sources, but other nutrients in general, and their impact on the development and severity of the disease, because we have seen that fertility is such a big influence on this disease. We don’t understand all the subtleties there. It’s becoming more and more of a problem so you see more effectiveness studies being done in universities and we’re starting to do more too.

“We have a lot to learn. At some point we will understand better. “

Always read and follow the directions on the label.

Honor, Intrinsic, Insignia, Xzemplar, Lexicon, Maxtima and Navicon are registered trademarks of BASF.

© 2021 BASF Group. All rights reserved.

Note: Any sale of products after registration is based solely on the EPA-approved label, and all information on product safety and effectiveness is addressed solely through the label.