Rain Returns! 1st Brown Patch, Dollar Spot, Waitea Patch, Crabgrass Tillers and a July 12 Field Day

It rained! It was getting very dry in the Chicago landscape. And then it all changed. In one night, July 4th, a good rain (over an inch) happened. Accumulated precipitation during July’s first week is now over 2 inches in most suburbs. You should have heard a collective sigh of relief from the trees, shrubs, turfgrass and me. Nevertheless, scars from a bone dry June are still evident — injured turfgrass usually takes 7-14 days to heal. In other words, damage from midday wilt and/or localized dry spot (LDS) on sand-based root zones (tees and greens) is still with us. Important to note: After the fact, LDS is often confused with fungal diseases. Just pick one that has a patchy look.

Image 1. Given mowing height and color, a bentgrass green contrasts nicely with a Kentucky bluegrass rough and native areas (hillside), Harborside International Golf Center, Chicago. Settle, Jul 6, 2022

In the landscape and on the golf courses one aspect that is now apparent are annual flower beds. Typically reaching full flowering in mass plantings by July 4th (red, white and blue always a nice color palette). Meanwhile, the shift to wet weather has meant turfgrass managers are now out scouting for midsummer diseases. For example, golf course superintendents and staff knew brown patch, was due — they just feel it in the air (warm, humid environmental conditions). By mid-week our (collective) scouting efforts paid off and 1st reports were coming in. Brown patch, Rhizoctonia solani, is our second most common foliar disease that we deal with (dollar spot is number 1). Nearly all cool-season turfgrass is susceptible. All it takes is a minimum leaf wetness duration of 10 hours of leaf wetness and warm nights (when minimum temperatures stay in the 70s). All that prose on summer foliar fungal diseases really means two things. Keep up your daily pest scouting and drink plenty of water as we now ease into the hot, humid dog days of summer.

Weather Recap (July’s 1st full week) by Shehbaz Singh, MS

Air Temperature. Chicago’s weather during the first week of July was warm and humid. The air temperature ranged from 64 to 85 °F. In 2021, temperatures for first week of July were lower than what we are experiencing now.

Figure 1. Chicago air temperatures (blue bars) versus normal range (brown band) in June, 2022.

Rainfall. Chicago saw good rainfall accumulation during the first week of July. The total rainfall accumulation up to this point averaged 1.6 inches which is quite higher than the normal accumulation of 0.7 inches. Heavy rainfall events occurred on July 4th and July 5th. In 2021, Chicago had no rainfall event during the first week of the month.

Figure 2. Accumulated rainfall in Chicago (green line) versus normal (brown line) in July, 2022.

Weather Forecast. Next week will be predominantly sunny. Partly cloudy conditions to prevail during first few days of the week. The air temperature will range from 67 to 88 °F. Chances of rainfall are low during the week, but the humidity will be higher than 50% on most days.

1st Brown Patch (Rhizoctonia solani)

Our first reports of brown patch occurred as we entered the weather typical of Chicago’s environment. Overall, this region displays a cool, humid environment based on temperature (the days are above 50 degrees from May to September) and annual rainfall (36.82 inches per year). But not so fast. In summer Chicago can quickly turn into a hot, humid climate (90s occur on average about 21 days a year). Brown patch is a disease that is limited to warm periods of summer — only occurs during hot, humid conditions.

Cultural Control. Good drainage is arguably most important in reducing brown patch and all Rhizoctonia-related diseases. Irrigation practices are second, third and fourth on the list. You get the message. Understand how to time automatic irrigation cycles.

Image 1. Symptoms of brown patch negatively impacting a RTF tall fescue tee at Bob Berry Sunshine Course in Lemont, IL. Settle, Jul 6, 2022
Image 2. Close up of brown patch damage on a tall fescue tee. Notice it is difficult to see distinct foliar lesions at low mowing heights. Settle, Jul 6, 2022
Image 3. A brown patch/Rhizoctonia solani lesion is distinctive on tall fescue at rough/lawn height: A tan center with irregular margins that are chocolate brown in color. Settle, Jul 6, 2022
  • Avoid watering in the evening hours = you are just extending the natural leaf wetness of dew and guttation that occurs at night (assume natural leaf wetness begins at ~midnight)
  • Time irrigation for the early morning hours = to help reduce conducive environmental conditions for brown patch (a leaf wetness period of 10 hours or more is required for its development)

Chemical Control. Many fungicides are labeled for brown patch. Applications can be made both preventively and curatively. Best control is achieved by preventive fungicide timing (before a disease outbreak). Read the label.

Dollar Spot of C3 Turfgrasses (Clarireedia jacksonii)

Dollar spot rapidly returned this week. It is not uncommon to see both dollar spot and brown patch active together during summer periods in the upper Midwest (when humid conditions exist). This is because most cool-season (C3) turfgrasses are susceptible to both diseases. It should be said that turfgrass breeders have gone to great lengths to improve the genetic resistance to dollar spot. It has taken decades. And it has worked! Why it’s so important to use newer varieties of turfgrass when possible. Step 1: Do your homework and find out the best dollar spot resistant turfgrass cultivar that is adapted for your area. Step 2: Buy the dollar-spot resistant turfgrass seed.

Image 1. Shehbaz Singh investigates our 1st dollar spot we’ve seen so far in the Kentucky bluegrass rough, Bob Berry Sunshine Course, Lemont, IL. Settle, Jul 6, 2022
Image 2. Close up of dollar spot damage on a Kentucky bluegrass rough. Notice spots are larger at higher mowing heights. Settle, Jul 6, 2022
Image 3. A new study is initiated to look at the curative performance of fungicides on dollar spot in a rough. An individual 4 ft by 6 ft treatment plot is shown. Study sponsor: PBI Gordon. Settle, Jul 6, 2022

C3 Turfgrass vs. Dollar Spot Recap

  • Use newer turfgrass varieties/cultivars that are bred to have better resistance to dollar spot disease whenever possible
  • Check out the new tool called Turfgrass Trial Explorer to gain access to over 1 million National Turfgrass Evaluation Program (NTEP data records from 1981–2020 at ntep.org/database.htm

Waitea Patch or Brown Ring Patch (Waitea circinata var. circinata)

Another Rhizoctonia disease has resurfaced. Though we are not allowed to call this one Rhizoctonia. Instead the name it was assigned is Waitea.

If you were scouting, you may have noticed the bright yellow rings have reappeared on sand-based golf greens this week. It is just another sign that conditions are once again conducive for foliar fungal diseases of turf. This one, Waitea, has been coming and going since about May. We generally do not see Waitea patch active in the hottest summer months of July and August because is naturally suppressed by summer’s peak heat. It is a sign that the very hot temperatures (90s for highs and even 100 degrees) which we experienced earlier in June have ebbed for now in Chicago. Cloud cover has cut the intense heat — for now.

Image 1. Some will argue that Waitea patch is largely an aesthetic disease because actual damage to putting surface characteristics is minimal. Nevertheless, it is a common disease May-June in Chicago. Midsummer heat naturally suppresses this fungal disease which causes symptoms of bright yellow rings. Settle, Jul 6, 2022
Image 2. Closeup of Waitea patch on a creeping bentgrass/Poa annua green. Notice the Poa component (light green) is most noticeable/susceptible. Poa annua turns a bright yellow color when leaf sheaths are infected by Waitea. Settle, Jul 6, 2022

Control. Most fungicides will provide control of Waitea patch (also known as brown ring patch). Read the label.

  • Do nothing and Waitea patch will go away naturally — summer peak heat suppresses its development
  • Contact fungicides may not provide as efficacious control of Waitea — site of infection is the leaf sheath
  • Thiophanate-methyl is not recommended — it is known to exacerbate/increase Waitea patch

Smooth Crabgrass (Digitaria ischaemum)

The development of crabgrass continues following our initial discovery of its germination in thin/open areas of turfgrass about a month ago. We are now beyond the 1–5 leaf stage (small size) and have begun to see tillering (larger size development). Post-emergent herbicide control of crabgrass is most effective when plants are smaller (1–5 leaf stage). Nevertheless, crabgrass will continue to germinate whenever warm, moist soil conditions exist during summer and why two applications spaced 28 days are useful in post-emergent control strategies of crabgrass.

Control. Spring-timed preemergent applications are most preferred and best. Nevertheless there are always skips in spreader patterns or lower than useful rates that occur. Also, certain areas (steep mounds in roughs for example) are not conducive for making applications.

Image 1. Crabgrass development has been occurring in Chicago for about a month. Settle, Jul 6, 2022
Image 2. A Post-emergent crabgrass study. Light green crabgrass is seen in four 4 ft by 6 ft individual untreated plots (foreground) versus control in twelve 4 ft by 6 ft herbicide (Q4 Plus) treated plots (background). Study sponsor: PBI Gordon. Settle, Jul 6, 2022

July 12 Field Day at the Bob Berry Sunshine Course

Please consider attending the upcoming field day in Lemont, Illinois. This will be the first field day in several years. More importantly, it is the first field day since the renovation and rededication of the three hole golf course on June 11, 2021. Sunshine Course was renamed the Bob Berry Sunshine.

Active Studies in 2022 on Bob Berry Sunshine Course Include:

  • CDGA/USGA Divot Study
  • Dandelion Weed Control
  • White Clover Weed Control
  • Henbit Weed Control
  • Teasle Weed Control
  • Yellow Nutsedge Weed Control
  • Crabgrass Weed Control
  • Herbicide Tolerance of Creeping Bentgrass
  • Dollar Spot Control
  • Brown Patch Control
  • Pythium Blight Control
Come See What’s New! The Bob Berry Sunshine Course was renovated and rededicated on June 11, 2021.
CDGA & PBI-GORDON FIELD DAY! To attend, please click here https://www.pbigordonturf.com/Chicago/

Final Photo

Angelonia and Begonia shine: Annual flower beds peak about midsummer each year in Chicago, Evanston, IL. Settle, Jul 3, 2022

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CDGATurfgrassProgram

CDGATurfgrassProgram

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Dedicated researchers and turf pathologists working for golf course superintendents in the Chicago area.