Gray Leaf Spot Development in Tall Fescue
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Collapse ▲Gray leaf spot has appeared in NC. This disease is difficult to control because the fungus thrives when nighttime temperatures stay above 72°F and produces many spores. We typically see about 28 days of suppression with fungicides for brown patch; however, this is not always true for gray leaf spot, unfortunately. There are effective management options for gray leaf spot, but achieving 28 days of protection is challenging during a summer like this one. Fungicides last only 12 to 14 days on the leaf when temperatures exceed 86°F. Under current conditions in NC, a fungus like the gray leaf spot pathogen can initiate new infections within 2 days. Below is a table listing fungicides labeled for gray leaf spot that can be used in a residential setting. The fungicides marked with ++++ are effective even under high pressure.
Fungicides can also be quite specific, so make sure that the issue affecting the lawn is actually a disease. Several factors contribute to the decline of tall fescue during the summer months. Don’t always assume it’s due to a fungal infection. Just because you see a few leaf spots here and there doesn’t mean that disease is the primary issue. We are experiencing a very tough summer here in NC. Don’t discount the stress created from prolonged heat, especially in waterlogged or droughty soils. This is magnified in lawns that were seeded at too high of a rate the prior fall as well. If you’re unsure, contact your local county extension office for assistance. They can also provide management advice and assist you in submitting samples to our lab for disease diagnosis, if needed.
After you confirm that you’ve correctly identified the disease, you can create an effective management plan. Below are the three most common diseases in tall fescue; brown patch, gray leaf spot, and Pythium blight. We’ve also included another image of a gray leaf spot trial from 2024, which shows a large area of dead turf. There is gray leaf spot present, but a large area died due to waterlogging and heat stress, which is a common recurrence across much of the state this year.
The three most common diseases of tall fescue, brown patch, gray leaf spot, and Pythium blight. An accurate disease diagnosis is crucial for fungicides to work properly.
A gray leaf spot trial at Lake Wheeler. There is gray leaf spot in this trial; however, the large dead area is primarily due to heat and waterlogging, which essentially cooked the turf.
Gray Leaf Spot Suppression with Fungicides:
| Fungicide and Formulation1 | Amount of Formulation2 | Application Interval (Days)3 | Efficacy Rating | Resistance Risk | FRAC Code4 |
|
azoxystrobin (Heritage) WG |
0.2 to 0.4 1 to 2 2 to 4 lbs |
14 to 28 14 to 28 14 to 28 |
++ | High | 11 |
| azoxystrobin + propiconazole (Headway) EC G |
1.5 to 3 2 to 4 lbs |
14 to 28 14 to 28 |
++++ | High | 11/3 |
| azoxystrobin + propiconazole (Compendium) | 1.3 to 2.6 | 14 to 28 | ++++ | High | 11/3 |
| cyazofamid + azoxystrobin (Union) | 2.9 to 5.75 | 14 to 28 | ++ | High | 21/11 |
| fluopyram + trifloxystrobin (Exteris Stressgard) | 2.1 to 6 | 14 to 28 | ? | High | 7/11 |
| fluoxastrobin (Fame) | 0.2 to 0.4 | 14 to 28 | ++ | High | 11 |
| flutolanil + thiophanate-methyl (SysStar) | 2 to 3 | 14 | +++ | High | 7/1 |
| metconazole (Tourney) | 0.37 | 14 | ++ | Medium | 3 |
| myclobutanil (Eagle) | 1.2 to 2.4 | 14 | ++ | Medium | 3 |
| propiconazole (Banner MAXX II) | 1 to 2 | 14 | ++ | Medium | 3 |
| pyraclostrobin (Insignia) WG SC |
0.5 to 0.9 0.4 to 0.7 |
14 to 28 14 to 28 |
++ | High | 11 |
| pyraclostrobin + fluxapyroxad (Lexicon Intrinsic) | 0.34 to 0.47 | 14 to 28 | +++ | High | 11/7 |
| thiophanate-methyl (3336 F) (3336 Plus) (3336 G) |
4 to 6 4 to 8 6 to 9 lbs |
14 14 to 28 14 |
++++ | High | 1 |
| triadimefon (Bayleton) | 0.5 to 1 | 14 | ++ | Medium | 3 |
| trifloxystrobin (Compass) | 0.15 to 0.2 0.25 |
14 21 |
++ | High | 11 |
| trifloxystrobin + triadimefon (Armada) |
0.6 to 1.5 | 14 to 28 | +++ | High | 11/3 |
| 1 Other trade names with the same active ingredients are labeled for use on turfgrasses and can be used according to label directions. 2 Units are oz, fl oz, or lb depending on formulation. Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications. 3 Use shorter intervals when conditions are very favorable for disease. 4 Fungicide Resistance Action Committee code. Products with same code have the same mode of action and are in the same chemical class. |
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| Efficacy Rating ++++ = excellent control when conditions are highly favorable for disease development +++ = good control when disease pressure is high, excellent control when disease pressure is moderate ++ = good control when disease pressure is moderate, excellent control when disease pressure is low + = good control when disease pressure is low ? = not rated due to insufficient data |
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| Resistance Risk Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application ? = not rated due to insufficient data |
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