Hello,

Based on your images the disease appears to be either Necrotic ring spot — Leptosphaeria korrae or Summer Patch — Magnaporthe poae

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Necrotic ring spot — Leptosphaeria korrae

General: Necrotic ring spot first appears as small patches 6 in. to 1 ft (15 cm to 0.3 m) in diameter. When the fungus is actively attacking the Kentucky bluegrass plants in the fall of the year, dark red blades of grass can be seen in the patches. The pathogen attacks root systems in the spring and fall, and in the summer, infected plants begin to wilt in patches. Patches eventually turn straw-colored, and older patches (2 yrs +) appear as a "frog-eye" with a center of healthy turf surrounded by a ring of dead turf.

Necrotic ring spot occurs in the cool regions of the world where Kentucky bluegrass (a primary host) is grown. The fungus achieves maximum growth at temperatures between 68° and 82° F (20° and 28° C). The pathogen is active in the cool weather of the spring and fall, even though symptoms are seen in the warm weather of the summer. The fungus is thought to move among the turf stand by growing along the surface of roots and rhizomes.

Cultural:

Summer symptoms are the result of the inability of the turfgrass to take up adequate amounts of water during the summer stress period because the fungus has destroyed the root system during the cool weather. One way to keep the weakened plants alive during the summer is through the use of light, daily irrigation. Turf should be irrigated daily with between 0.1 and 0.2 in. (0.25 and 0.5 cm) of water, preferably applied between noon and 4:00 P.M. This rate can be doubled during periods of prolonged droughts.

Adequate levels of nitrogen should also be used in the management of necrotic ring spot. Improved Kentucky bluegrass cultivars require 4-6 lb (2 to 2.9 kg) of actual nitrogen per 1000 ft2 (100 m2) per season. Slow-release nitrogen fertilizers such as Turf Restore, Nature Safe, Lawn Restore, IBDU, UF, etc, are more effective in managing the disease than fast-release fertilizers like urea. Complete fertilizers (N-P-K) with slow-release nitrogen carriers are the most effective.

Chemical:

Curative: The thiophanate methyl and azoxystrobin fungicides provide the best curative management. To be effective, these fungicides need to be drenched into the soil before they dry on the foliage so that they are translocated upward from the roots. Best results are obtained when the turf is irrigated before the fungicides are applied.

Preventive: The DMI fungicides such as fenarimol, myclobutanil, and propiconazole work best preventively. These fungicides are translocated in both directions and do not have to be drenched into the soil to be effective. Unless adequate nitrogen is applied, these fungicides will not be effective.

Disclaimer: Always read, understand, and follow the label directions. Mention or exclusion of specific products does not represent an endorsement or condemnation of any product by Michigan State University.

Hosts:

Turfgrass hosts include Kentucky bluegrass, fine-leaf fescue, annual bluegrass, and rough bluegrass.

The above information is located at this link: http://www.msuturfdiseases.net/details/_/necrotic_ring_spot_13/

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Summer Patch — Magnaporthe poae

General: Summer patch first appears in the warm weather of summer as yellow to bronze-colored, irregular-shaped patches ranging from 6 in. to 3 ft (15.3 cm to 1 m) in diameter. Patches may coalesce, resulting in areas of affected turf that are several feet in diameter. Annual bluegrass is the predominant host, and in mixed stands such as golf course greens, fairways, and tees, a "frog-eye" symptom can be seen with creeping bentgrass remaining healthy. Dark "runner hyphae" is evident on crowns and roots of affected plants when observed microscopically.

The disease first appears in the warm weather of the summer, typically after rainy periods or heavy downpours. Saturated soils have been shown to exacerbate disease development. Soil temperatures above 70° F (21.1° C) at a 2 in. (5cm) depth for at least 48 hours are key for disease onset as well. While symptoms are present in the warm weather, the infection takes place in the spring when soil temperatures first reach 65° F (18.3° C) at a 2 in. (5 cm) depth. Weakened roots from saturated, anoxygenic soil conditions allow for further infection and symptom development.

Cultural: Fertility is an important management aspect for summer patch. Having adequate levels of all major soil nutrients can be determined by soil testing with the exception of nitrogen. Adequate levels of nitrogen are essential in managing summer patch. Moderate levels of nitrogen such as 0.5 lb of nitrogen per 1000 ft2 (0.25 kg per 100 m2) once a month are required for adequate summer patch management.

Light, daily irrigation in amounts ranging from 0.1 to 0.4 in. (0.25 to 1.0 cm), depending on rainfall, temperature, and evapotranspiration, will help reduce the severity of the summer patch. Irrigation timing should be scheduled in the mid-late afternoon so as to allow adequate time for the turfgrass to dry before nightfall. This practice helps to cool off plants during the warmest part of the day, allowing susceptible turf to better survive summer stress.

Chemical: Summer patch is best managed by chemicals preventively. The timing of these fungicide applications must be timed properly in order to be effective in controlling summer patch. DMI fungicides, triadimefon, myclobutanil, fenarimol, and propiconazole, and the QoI fungicide azoxystrobin are effective but have to be applied before symptoms develop. Most recommendations are for an application when soil temperatures reach 65° F (18.3° C), with a second application made 30 days later. In problematic areas where summer heat lasts for more than three

months, an additional application may have to be made 30 days later.

Disclaimer: Always read, understand, and follow the label directions. Mention or exclusion of specific products does not represent an endorsement or condemnation of any product by Michigan State University.

Hosts: Turfgrass hosts include, but are not limited to annual bluegrass, Kentucky bluegrass, fine-leaf fescues.

The above information is also at this link:

http://www.msuturfdiseases.net/details/_/summer_patch_18/

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I recommend you get a confirmed diagnosis from the MSU Diagnostic Plant Lab

MSU Plant & Pest Diagnostics is no longer accepting walk-in consultations at this time. They are open for business for all samples that are dropped off or mailed to the lab. When submitting plant samples, they encourage clients to email digital images to accompany the physical samples. Images can be sent to <personal data hidden>.

From the lab: Please do not ship samples on Fridays. Due to the current COVID-19 circumstances, please allow additional processing time. Thank you for your patience and understanding.

There is a $20-25 dollar fee (if they need a sample sent). I am guessing that the lab will probably want a sample to look at under the microscope

Every sample must be accompanied by a completed submission form. Please place the form in a separate resealable bag to prevent it from getting damp or soiled.

The form is at this link:

https://www.canr.msu.edu/pestid/uploads/files/MSU-DS-Form-012-001-version6.0.pdf

Complete details of submitting a sample are at this link: https://www.canr.msu.edu/pestid/submit-samples/

PLEASE REMEMBER THAT THE LAB WILL LET YOU KNOW WHEN YOU CAN SEND THE SAMPLE - AS I MENTIONED EARLIER, THEY WILL WANT TO EXAMINE YOUR IMAGES FIRST

Hope this helps!

Hello Dan,

For a live conversation - The number is <personal data hidden> and they are open 9:00 a.m. to 12:00 p.m. - Monday, Wednesdays, and Fridays (except holidays)