Review of Turf Pathology Fungicide Trials From 2020

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We had many interesting fungicide trials in summer of 2020 and we are looking forward to discussing some of the new and exciting products as they get closer to market. Overall, our fungicide testing trial program was down due to the coronavirus, yet we still had some very interesting trials. Most of what was submitted to our program were experimental materials and many performed quite well. One of the most exciting was an experimental material that completely suppressed Pythium root rot on creeping bentgrass. We were excited to see this because Segway by itself struggled some this year with the frequent rains since July. I know it is a tease to mention this material, but it is still early on in the discovery process and we are hoping it will continue to work its way to the market.

Curative Large Patch Control

We examined the curative properties of a few fungicides for large patch in the spring. These products included an experimental from Syngenta, Ascernity, Armada, and Mirage. We started this trial when large patch was severe, averaging around 70% disease in the trial area! A single application of each fungicide was applied on March 25th and disease was quantified for the next 27 days.

Zoysiagrass
Typically, with this amount of disease, curative suppression will be limited at best. However, Syngenta’s experimental and Ascernity reduced large patch to 38% and 54% respectively. The non-treated control remained at 77% on average for the duration of the trial. We observed the reduction in disease over a 27-day period for the experimental and Ascernity only, but the experimental product showed curative suppression within 14 days of the application. Given these results, Ascernity and the new experimental will be staples for large patch management in warm-season grasses. Armada and Mirage did not suppress large patch curatively, however these products have performed well in preventative large patch trials in the past. As a reminder, preventative applications for large patch should start in the fall when soil temperatures drop to 80oF for centipegrass and St. Augustinegrass and at 70oF for zoysiagrasses.

For more information about large patch, please consult the following: Large Patch Management & Control

Dollar Spot Management in NC Mountains

For the second year in a row, we conducted a dollar spot trial at Hound Ears Club in Boone, NC. Although we observe excellent dollar spot pressure in Raleigh, we have been conducting trials in the mountains to demonstrate fungicide efficacy in a real-world environment. Moreover, many courses in the NC mountains have documented resistance to propiconazole which adds another interesting twist to the trial.

Creeping Bentgrass fairways

This year, we examined a few dollar spot programs from BASF and they performed well. All of the program treatments suppressed dollar spot when compared to the untreated control plots. This is typical of what we have observed in the past that stand-alone products may not perform well in this environment. Maxtima, BASF’s new DMI, has continued to provide excellent dollar spot suppression which was evident in this trial.

For more information about dollar spot, please consult the following: Dollar Spot Management & Control

Gray Leaf Spot Management in Tall Fescue

Gray leaf spot was problematic in 2020 on tall fescue swards. This disease continues to ravage tall fescue and we are still searching of a viable strategy to manage this disease.

Tall fescue

The images clearly show a promising experimental product from Syngenta, but also demonstrate that mixtures such as Ascernity and Headway performed well in terms of gray leaf spot suppression. Nothing provided 100% control, so next year we will have to investigate a programmatic approach to gray leaf spot management. Given the severity of gray leaf spot recently, Headway should strongly be considered as a backbone in a tall fescue fungicide program.

For more information about gray leaf spot, please consult the following: Gray Leaf Spot Management & Control

Effect of Post-Application Irrigation on Pythium Blight

Finally, we conducted an interesting greenhouse trial early in 2020 on Pythium blight management in perennial ryegrass. The goal of this trial was not to see if Segway or Union would perform well on Pythium blight, but rather to see if post-application irrigation affects control.

Pythium blight

Not surprisingly, excellent products such as Segway or Union provided exceptional Pythium blight control regardless of whether they were irrigated in or not. Although we did not see differences between the Segway treated pots and Union treated pots, Union over all had less disease. This was to be expected given Union is a combination of cyazofamid and azoxystrobin. This trial provides further evidence that irrigating fungicides in does not affect foliar disease control.