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The time for the second application of fungicides on the new ​bentgrass research at the ISU horticulture research station has arrived. Chris Blume and I applied the curative, second treatment of Emerald® (boscalid) and Daconil® (chlorothalonil) today, August 18, 2009. The new bentgrass research is focusing on the susceptibility of different cultivars of bentgrass to the disease dollar spot. In the study, each plot is split, one side receiving no fungicides, while the other is treated with both a preventative and a curative application of boscalid and chlorothalonil. This year has proven to be an excellent year for dollar spot out at the research station and many of our bentgrass areas are spotted with the disease.

The disease dollar spot is caused by the fungal pathogen Sclerotinia homoeocarpa. This disease commonly infects many of our cool-season grasses. Dollar spot is a particular concern on bent/poa greens where the sunken pockets may interfere with putting quality. Dollar spot can develop over a wide range of temperatures (55-80°F) when the dew persists for long periods of time (longer than 8 hours). Dollar spot is also considered a low nitrogen disease and is most severe on nitrogen deficient stands of turf.

The pathogen causes blighted, circular patches of turf which are similar in size to a silver dollar (rarely larger than 2 in. in diameter) on low mown areas, and up to 6 in. or more in diameter on taller mown areas. The blighted spots of turf often occur in clusters and may merge together to produce larger blighted areas as disease development progresses. Active dollar spot infections produce a cottony white mycelia mass that is often evident on the turf during the early morning hours. When viewed under a microscope the mycelium will exhibit y-shaped branching and the presence of septum unlike the mycelia of pythium that are void of septum. In addition to the mycelia mass that may be visible, this pathogen also causes leaf lesions that have light tan centers and a red-brown margin. The leaf lesions of dollar spot are more commonly observed on taller turf species, such as Kentucky bluegrass, where the lesions take on the shape of an hour glass.

There are many ways to control dollar spot. One important management technique is to implement a satisfactory nitrogen fertility program. Nitrogen deficient stands of turf are more susceptible to dollar spot outbreaks. However, over stimulating with nitrogen may increase disease pressure from other, less desirable, diseases. Another option in control is to choose a less susceptible cultivar. Although there are no completely resistant cultivars of bentgrass, there are cultivars that are more resistant than others. For example, the cultivar Crenshaw® is far more susceptible to dollar spot than the cultivar Declaration®. Irrigation practices that limit the duration of leaf wetness will also help limit the occurrence of the disease. There are also fungicides available for the control of dollar spot. These fungicides often require multiple applications to effectively control this disease. Also, fungicides that are classified as site specific inhibitors have a high risk of resistance development and their repetitive use should be avoided. Some effective fungicides are Emerald®, Daconil®, Curlan®, and Tourney® along with many others.

Nick Dunlap

We are testing a variety of plant growth regulator products and fungicide chemistries for efficacy on early spring seedhead control and possible disease reduction. This study is being conducted on a fairway mixed stand (50/50) of Poa annua and creeping bentgrass and has been initiated to show visual turf quality differentiation of the various products. Last season, test strips on a nursery green at North Shore Country Club in Glenview, IL showed considerably less disease when a plant growth regulator, Embark, was applied once during June. The early season applications as seen in the bar graph below for “Visual Quality” are at 21 and 28 days after treatments (DAT).

The first application was critically timed to coincide with forsythia bloom on April 14th. There are three Embark treatments all at the 40 oz/acre rate; Embark alone, Embark with Primo 0.125 fl oz/M and Embark with Primo 0.125 fl oz/M and also Signature 4 oz/M. This series of Embark treatments was only administered as a one time application due to a high amount of tip burn on the creeping bentgrass and chlorosis on the Poa annua. All treatments were within labeled rates. The result is poor visual quality of turf in this early spring period. However, all of the Embark treatments were excellent at eliminating all Poa annua seedheads (100% control).

Two combinations of Proxy and Primo (5 fl oz/M + 0.125/M) were tested, at a 21 day interval with one including Signature at the 4 oz/M rate. However, neither of the two mixes resulted in greater seedhead suppression than any Embark combination (see graph). The visual quality for the Proxy + Primo + Signature yielded better quality at both the 21DAT and 28DAT (7 days after second application), but interestingly, there was no statistical differences between the treatment that contained only Proxy + Primo and any of the Embark treatments.

So, the question that is brought to my attention from the data is whether there is some sort of synergistic effects in mixing Proxy + Primo + Signature? On the flipside, we don’t see any of these effects in tank mixing with Embark, so this means we can rule out that it may have had something to do with a pigmented spray or not. Secondly, will the sacrifice in early season turf quality using Embark pay off when we get to the heat of the summer? And lastly, is it worth the dollars to apply fungicide this early for dollar spot when we have very low disease pressure? Over the next few weeks, we will likely begin to start seeing dollar spot and I will be excited to see how these early season applications of plant growth regulators and fungicides function in producing good turf quality and resistance to disease.

Tim Sibicky
TSibicky@hotmail.com
Chicago District Golf Association
11855 Archer Avenue
Lemont, IL 60439

The Open Championship concluded over the weekend with first time major champion Louis Oosthuizen running away from the field for the victory. With three of the four majors completed the summer is off and rolling.

The Field Day Classic was held last week at Jewell Golf and Country Club. It was a great day despite the heat with temperatures reaching into the high 90’s and a heat index well over 100. The course was in great shape and the weather didn’t seem to hinder low scoring. Special thanks to Brian Abels and his entire staff for hosting and putting on a great event.

The hot temperatures have also been causing havoc to our cool-season turfgrasses as well. Soil temperatures are now reaching into the low 80’s causing root growth to stop. Research has shown that creeping bentgrass generally loses about three quarters of its root biomass from the end of May to the beginning of June. This natural root decline coupled with the extreme rainfall amounts during the month of June which caused roots to pull back has resulted in turf that is especially sensitive to environmental and fungal stresses.

I have seen Kentucky bluegrass beginning to decline over the last couple of weeks. The pictures below show a low-mow Kentucky bluegrass intermediate rough. After inspecting the area, the decline seemed to be the result of leaf spot/melting out disease. The disease activity was also more prevalent where the turf was under shade part of the day. Notice how the common type Kentucky bluegrass in the primary rough remains largely unaffected. Mowing height also appears to be playing a large role in the disease activity. Leaf spot can be controlled on a curative basis but applications are most effective in the early stages of the disease.

Diseases will continue to wreak havoc on our cool-season grasses the rest of the summer. For those of you with large acres of perennial ryegrass, the prime window for gray leaf spot is right around the corner.

On a side note, Ames and central Iowa had severe storms roll through Saturday night with winds reaching speeds of over 70 mph. While I kind of like severe weather I do not enjoy the cleanup. Waking up Sunday morning it looked like a bomb had went off in the neighborhood with plant debris and trees down everywhere. Luckily the picture below wasn’t from my house but wasn’t too far away. Hopefully the rest of you in central Iowa were able to avoid damage as well.

Enjoy the first part of the weekend before warmer temperatures move in on Sunday and early next week. Here is your list of links to articles regarding turf. Have a great weekend!

MSU Turfgrass Field Day: 8/18/10. The 2010 MSU Turfgrass Field Day is open to all turf professionals regardless of affiliation. Spend a day with the experts and see what cutting edge research can do to make your operation more productive and profitable. We look forward to seeing you there! http://www.michiganturfgrass.org/msu-turfgrass-field-day;-8182010;-golf-course-turfgrass-field-day-140/

Canadian Tour Will Help USGA Test Shorter Golf Balls. Many of the game's experts - most prominently Jack Nicklaus - argue for dialing back golf ball technology as a way to reverse distance gains they believe are bad for the game's future and dismissive of the game's past. Where do you fall in the debate over distance in golf? http://golf.about.com/b/2010/07/24/canadian-tour-will-help-usga-test-shorter-golf-balls.htm

Why We Need More Par-Three Courses. Mike Keiser, who commissions everything at the Bandon Dunes complex in Oregon as a golf purist's fantasy, is building a fifth course to add to his famous four. It's something you don't hear about much anymore—a par-three. Construction on the 12-holer, tentatively called "The Bandon Preserve," starts in February. http://online.wsj.com/article/SB10001424052748703467304575382941326891262.html?mod=googlenews_wsj

Golf Course Superintendents Embracing Social Media. Last Thursday, course superintendent Frank Tichenor arrived at work before dawn to discover a potential nightmare: hyperodes weevil. Naturally, Tichenor’s first reaction was to grab his BlackBerry ... and take a picture for his blog. “There’s always something happening on the golf course,” Tichenor said. “So I took a picture of it, put it up on the blog, and tweeted it and said, ‘Look, this is what’s happening and this is how we’re going to handle it.’ ” http://www.golfcourseindustry.com/gci-07261-superintendents-social-media.aspx

Kansas Turfgrass Field Day. Kansas Turfgrass Field Day, Thursday, August 5, 2010, Rocky Ford Research Center, Manhattan, KS, 8:00 a.m. – 1:30 p.m. Cost: $30.00 (includes lunch), For more information, go to: http://www.hfrr.ksu.edu/DesktopModules/ViewDocument.aspx?DocumentID=2840

Bentgrass and Poa annua greens are hard-hit. Sometimes conditions can become so oppressive on a given site that it overwhelms creeping bentgrass and causes rapid decline, despite the heroic efforts of the superintendent and staff. This information in this article is designed to focus on what can be done amidst this difficult summer. http://www.usga.org/course_care/regional_updates/regional_reports/southeast/Summer-2010---Bad-To-Worse-For-Creeping-Bentgrass---July-2010/

A detailed labor analysis is effective for tracking costs and making decisions. Golfers, owners, and course officials often have a difficult time understanding how it can take so many people to perform a relatively simple task. So, how many people does it really take to maintain a golf course? Here is the definitive answer: It depends. Accurately forecasting such emergencies is difficult, if not impossible. Read on for a step-by-step procedure showing how to perform a labor analysis at your course. http://turf.lib.msu.edu/gsr/2010s/2010/100524.pdf

The career assistant superintendent. It is a tough time to be an assistant superintendent of a golf course in the present job market and economy. It seems to me that if you are fortunate enough to have a job right now, you are holding on to it and riding out this ugly wave. http://www.golfcourseindustry.com/gci-080210-guest-column-jeff-wichman-career-superintendent.aspx

Warmer temperatures this week have provided suitable environmental conditions for dollar spot (Sclerotinia homoeoecarpa) development on fairways. We are now beginning to see a late season surge in damage as we enter the autumn months. Thinking back to the beginning of the 2010 season, we set out to investigate the effectiveness of early season dollar spot programs and if you look (Figure 1) we are able to see the progression of the disease at a variety of different locations surrounding Chicago. So I ask, was it worth it to spray early in April-May? At our locations for this year’s Biorational study, ranging from North Shore Country Club in Glenview, IL Coyote Run Golf Course in Flossmor, IL and Briar Ridge CC in northwest Indiana, it is evident that the disease failed to take off until the middle of summer.
 

As an additional note: each of our locations vary in turfgrass composition with Coyote Run having a blend of Southshore and L93, Briar Ridge CC with Penncross and North Shore CC having a mix of creeping bentgrass and Poa annua. We tested seven treatments, Rhapsody 10 fl oz, Ecoguard 20 fl oz, Dew Cure 4.0 fl oz, Urea 0.15 lbs, Daconil 3.2 oz, Daconil 3.2 oz curative (as needed using 5% damage threshold).

Treatments are being applied at 14 day intervals at label rates and the plots at all locations are scouted weekly. If disease infection centers exceed an average of 5% area affected a curative application of 3.2 oz of Daconil is applied over the biorational treatment. We are able to understand the effectiveness of the different treatments by comparing visual quality, percentage of disease, and number of curative fungicide applications. Our goal is to reduce fungicide use and maintain turfgrass quality at levels required for fairways.

Results (Table 1). At Coyote Run GC, we have been able to maintain the Dew Cure treatment below the 5% threshold without applying a single curative application of Daconil! At this location we were also able to see a recuperative effect within the Urea treatment, only requiring a single application. At North Shore Country Club we were able to reduce the curative applications by two when using DewCure. All other plots required the same amount of curatives, four apps. At Briar Ridge with DewCure, we were able to reduce the number of curative required by one. At Briar Ridge we did observe phytotoxicity by DewCure. On August 10 an application of all products were made at a time when temperatures were 90+ degrees and turf was entering drought stress. This resulted in severe injury by DewCure alone.

These biorational products may play more important roles in disease management programs as we continue to progress into a reduced input future. As we continue to learn and understand the benefits and limitations, superintendents will be able to make better and more informed decisions. We may as well investigate alternatives now before we run out of options.

The final picture shows a plot treated with Dew Cure resisting dollar spot without receiving any curative applications during the summer of 2010 at Coyote Run GC.

Tim Sibicky
TSibicky@cdga.org
Chicago District Golf Association
11855 Archer Avenue
Lemont, IL 60439