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North Central Region Collaborative Effort...and the data says

Dollar spot was the talk for the last two weeks of September, but now the night temps will hold off any development except for a possible warm spell left in the year. Now is the time to look back and evaluate our dollar spot information. We had a chance to evaluate our new fairway bentgrass variety trial during the highest disease pressure of the season. The borders of ‘Alpha’ and several entries were lighting up! It has been a long road for this trial. Twenty nine bentgrass
varieties were seeded last year and then reseeded this May. Now we have lowered the height (0.75 inches) slowly over the summer and finally we got some disease.

Next year we will learn (again)
Next year we will get a better idea for disease resistance of these varieties. So far our variation is still large and another years worth of data will be needed to determine the genetic resistance in the new varieties like ‘CY-2', ‘Kingpin’, ‘Shark’, and ‘007’. This data does show that varieties have been released with comparable resistance to ‘L-93’. Hopefully with more time we can say that there are a handful of varieties with greater resistance than ‘L-93’. In National Turfgrass Evaluation Program (NTEP) trials, ‘Declaration’ has shown promise. ‘Alister’ is actually a colonial bentgrass species. In previous research on Sunshine Course, colonial varieties are damaged by brown patch and weeds become a problem.

The “take home message”...
The goal of this research conducted here in Lemont and 11 other Midwestern universities is to determine how many fungicide sprays are needed when varieties with greater resistance are used.

The L-93 Story at North Shore
This year at North Shore Country Club we set out treatments on a fairway strip of ‘L-93’. Only one application was made on May 14 and the plan was to see which treatments provided the longest control. Bayleton, Emerald, Daconil, Banner Maxx, and Chipco GT were all applied and we waited for dollar spot. Mid June came around, and no dollar spot – too cold. The beginning of July came and only a tiny bit of dollar spot. The beginning of August came around and finally dollar spot reached 1-3%in all plots. Fungicide or not, all treatments were the same for percent dollar spot incidence and plot visual quality.

No differences...
We found no differences in our statistics. What did we learn? Maybe May 14 is too early for dollar spot control. Maybe we can reduce our fungicide inputs by utilizing genetic resistance and eliminating one or two applications early in the summer. Our heads are already spinning around to design research in 2010.

Emerald for next year’s research...
So far our thoughts are to pick one fungicide and apply on selected dates from May through June or July on each ‘L-93’ and a bentgrass/Poa mixture. This will give us an optimal timing for first application to control dollar spot on two different turfgrasses. For now we will write down our thoughts and continue to analyze the research.

Keith Rincker
KRincker@cdga.org
Chicago District Golf Association
11855 Archer Avenue
Lemont, IL 60439

This is a week that people in Central Iowa will not forget for a long time. Ames received around 10 inches of rain in a three day period and the city experienced arguably its most devastating flood ever. The Squaw Creek and Skunk River are the two major waterways that run through town. Squaw Creek crested at 18.13 feet (flood stage is 9) which was just shy of the record crest of 18.5 experienced back in 1993. The Skunk River crested at 26.52 feet (flood stage is 20) which was above the 1993 crest of 25.53 feet. For those familiar with Ames, the picture above is a shot of Hilton Coliseum inundated in flood waters.

The majority of the flood waters have now receded and cleanup efforts are well underway. Trying to predict the survival of turfgrass in flooded conditions is tricky business and depends on so many factors. Weather is a big factor and has not been on our side so far this week. Temperatures have been in the low 90’s with the humidity pushing heat indices into the 100’s.

We were greeted to a healthy dose of mycelium at our research station this morning. During my time spend in industry, I learned that trying to visually distinguish between dollar spot and pythium blight is very difficult (at least it is for me!) so we brought the sample to campus for a closer look. Inspection of the sample under a compound microscope confirmed that the disease we were seeing was in fact Pythium blight.
 

We also stumbled upon some slime mold. Earlier in the year we had a post about slime mold on green height creeping bentgrass. This slime mold appeared on rough height Kentucky bluegrass. Remember that slime molds are more of an oddity, they’re unsightly but they are not considered harmful and control measures are not necessary.

I’ll leave you with a video courtesy of KCCI News Channel 8 showing an aerial view of the city this past Wednesday morning.

https://www.youtube.com/watch?v=YQSnfvRw8mU

When I arrived to work this morning I was greeted by an outbreak of dollar spot. We had been on the dry side since the last week June but we received 1.33 inches of rain yesterday. The abundant rainfall coupled with the warm overnight temperatures, and high humidity led to conditions that were very conducive for dollar spot. Mycelium was especially abundant in our untreated creeping bentgrass areas.

Below are a few pictures from one of our creeping bentgrass fairway trials. This particular trial has 24 different cultivars of creeping bentgrass. Each plot is split in half and is either untreated or receives applications of Daconil and Emerald.

The objective of the trial is the determine the susceptibility of creeping bentgrass cultivars to dollar spot when maintained under reduced fungicide applications. Applications of the Daconil and Emerald mixture are scheduled based on a threshold of dollar spot severity in a cultivar with a high level of dollar spot resistance. Declaration is the indicator cultivar in this trial.

This picture shows the Declaration plot in one of the replications. The left half of the plot is the treated side and before today had only received one application on June 6. Declaration is a recently developed cultivar of creeping bentgrass that has relatively high resistance to dollar spot compared with other cultivars. Even the untreated side (right side) is holding up fairly well without receiving any fungicide to date.

This next picture shows a Penn A-4 plot. Here the right half of the plot is the treated side. As you can see, there are noticeable differences between cultivars of creeping bentgrass with respect to their disease resistance.

This trial along with many others will be on display during the Iowa Turfgrass Institute/Iowa State University Field Day on July 21. There is still time to register for the event.

Marcus Jones
Assistant Scientist

This summer at Des Moines Golf and Country Club, Director of Grounds, Rick Tegtmeier, CGCS and two ISU Interns conducted a fungicide study that compared name brand versus generic products for dollar spot control. The two interns from Iowa State University were, Tyler Boley and Tayler Riggen. They worked closely with Luke Dant from Syngenta Professional Products to set up a replicated study on the golf course.

How they did it
Plots were arranged on fairways at two different locations on the course in order to account for spatial variability. The fairways contain ‘Penneagle’ creeping bentgrass maintained at 0.5 inches. One set of plots were located on the north course and the other on the south course. Each set of plots was replicated three times. Treatments included an untreated control, Daconil WeatherStik, Manicure 6FL, and Echo 6F ETQ fungicides. All products were applied at a rate of 2 oz/1000 ft2, to deliver the same amount of active ingredient, using a backpack sprayer with #8002 flat fan nozzles. Carrier volume was 44 gallons/acre. Spray applications began on May 14 and concluded August 13. Applications were made on 14-day intervals for a total of 7 applications. Percentage of turf affected by dollar spot was visually estimated on July 1 and August 14.

What they found
Each plot in the study succumbed to some dollar spot, but it was clear there were differences between the products in our study (Table 1).

Similar trends were evident on each of the test plots between the north and south courses but the disease pressure on the north course was far more severe. An application of Bayleton was made to the plots on the north course on June 22 to help reduce disease pressure. The main findings from the study are summarized below.

- Control plots sustained significant damage and possibly needed reestablishment.

- All chemicals succumbed to some breakthrough if applied on 14-day intervals. At the rate used in our study, shorter intervals are needed with all products.

- Manicure 6FL seemed to have good control until approximately 10 days after each application. After that, there was significant breakthrough.

- Echo ETQ had less than desired control through the 14-day period between applications. Echo ETQ fungicide is green in color which is designed to help cool the turf and in turn help prevent disease. In our opinion, the green colorant has little effect and was barely noticeable after being sprayed.

- Daconil WeatherStik had acceptable control until 13 and 14 days after application, and then some small breakthrough was evident. Recovery was not exceptional, but due to better initial control of dollar spot, Daconil provided the best control of dollar spot.

- One option would be to compare prices of products to see if Manicure 6FL or Echo ETQ could be applied on 10 day intervals for lesser overall price, however; this would increase labor costs and wear and tear on spray equipment, possibly negating any cost savings by purchasing these generic products. In our study, Manicure and Echo provided nearly the same level of dollar spot control.

This is the first of the 2011 research reports. It includes the 2010 results from our trial on creeping bentgrasses maintained at both fairway and green height. Tables 3 and 4 are jpg photos and you will need to click on them to be able to read them.

Creeping Bentgrass Dollar Spot Study

Christopher J. Blume and Nick E. Christians

Objectives

The objectives of this study are to determine the susceptibility of creeping bentgrass (Agrostis stolonifera) cultivars to dollar spot (Sclerotinia homeocarpa) under both green height and fairway height.

Materials and Methods

This fairway height (0.5”) and green height (0.25”) studies are being conducted at the Iowa State University Turfgrass Research Station it is part of a regional project being conducted at several of the Midwestern Universities. Both studies included 24 cultivars, although some of the cultivars differed on the two sites (Table 1). The green-height study area was established on a sand-capped area, and the fairway-height area was established on a native soil area (Nicollet clay-loam).

Both studies were established 17 September, 2008. The plots were allowed to mature until the spring of 2009. The plots were then split into untreated and fungicide treated halves. The study was conducted as a randomized split block design, with three replications.

Fungicide treatment timing was based on the cultivar ‘Declaration’, which is the most dollar spot tolerant cultivar in the study. Treatments were made to the green height plots when ‘Declaration’ was observed to have at least 5% of the plot area infested with dollar spot. The fairway height study area was treated when ‘Declaration’ was observed to have at least 10% of the plot area infested.

The fungicide mixture consisted of Emerald (0.18 oz product/1000ft²) and Daconil Ultrex (3.2 oz product/1000ft²), applied in 2 gallons water/1000ft². The applications were applied using a modified spray boom, with two TeeJet XR flat fan nozzles. In 2010, three applications were made 24 June, 19 August, and 4 October.

Results

‘Memorial’ and ‘Penncross’, and ‘LS-44’ had the best quality ratings in the green height study in 2010, whereas ‘Allister’ received the lowest rating. In the fairway height study, ‘Alpha’, ‘LS-44’, and ‘Memorial’ were the highest rated cultivars, and ‘Independence’, ‘Declaration’ and ‘SR 1150’ received the lowest quality ratings (Table 2).

‘Century’ and ‘Imperial’ showed the most damage from dollar spot in both September and October in the green height study (Table 3). ‘Memorial’, ‘Declaration’, and ‘Crystal Bluelinks’ had the least damage in untreated plots at the end of the season.

There was not as much dollar spot in 2010 as there was in 2009 on the fairway height bentgrass. At the first two ratings of the season, there was more dollar spot in the treated side than in the untreated side of the plot. These plots had not been treated since the fall before. The reason for this observation is unknown. In August, no dollar spot was observed on treated or on untreated sides of the plot. In September, ‘Southshore’ and ‘Century’ had the most dollar spot on the untreated side of the plots, whereas ‘Memorial’, ‘Independence’, and ‘Declaration’ had the least dollar spot. In October, ‘Crenshaw’ and ‘Century’ had the most dollar spot and ‘Memorial’, ‘Alister’, ‘Pennlinks II’ and ‘Memorial’ had the least (Table 4).