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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

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 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).

In the next few weeks, I'm going to upload a series of posts from ISU students who have been working on research projects and from those who were on internships last summer. They submit written reports on their experience and many of these are excellent.

The post below is from an undergraduate named Steve Johnson. He worked for Mark Gleason in pathology this summer and established some trials at the research station. This is the second of three posts from him. The first was on Sept. 27. This is the second one and the third one will come in a few days.

Steve Johnson, Soph. Summer Intern Blog #2
 

In continuation from my first blog I will go over the methods I used to carry out the experiment. However, while the idea of improving disease ratings by using multiple raters to average the results was the primary purpose, useful information on the effectiveness of specific fungicides to combat dollar spot was also gained through the experiment. The overall idea was to rate and evaluate the effectiveness of 19 fungicide treatments against a selected fungus disease, dollar spot, at two locations and in the process improve the disease ratings by using two raters to average the results.

The first plot was located at the ISU Horticulture Farm near Gilbert, Iowa, and the second at an old golf green located just north of Roy J. Carver Co-Lab on the northwest edge of the Iowa State campus. This location was called the WOI green, since the former WOI-TV building is also located nearby. Turf cultivars were ‘Emerald’ at the Hort farm and ‘Washington’ at WOI. Four sub-plots were needed for each of the 19 treatments making 76 plots. Four more plots were added as a control and not sprayed, totaling 80 sub-plots per location.

The first step to setting up the experiment was creating the sub-plots. By using Pythagoras’ theorem, accurate plot dimensions were insured for both site locations. A method that uses nails and a ball of white string, which is represented by the pictures, was utilized so that the corners of every 5-ft x 4-ft subplot could be seen temporarily. Orange spray paint was then used to mark the corners of each subplot so that the string could be removed and the subplots could still be located. Re-spraying the subplot corners for both locations was necessary every few weeks, especially following a heavy rain. Assignment of the spray treatments to specific sub-plots at both locations was randomized and then marked on maps for both the Hort Farm and WOI.

After the individual plots were marked the Hort Farm plot was ready to be inoculated with dollar spot. The WOI plot was not inoculated. Rye grain seeds were infested with Sclerotinia homoeocarpa, the fungus that causes dollar spot, which were then spread evenly across the surface of the 80 sub-plots. The green was kept moist but not water- logged for five days without mowing to incite fungal growth.

Following the inoculation a spray calendar was made based on the experiment’s protocol. The first spray began on 7 June, except for treatments 18 and 19 which began 24 May, and ended on 17 August. Re-application of the fungicides depended on the protocol, which had varying spray intervals. Backpack sprayers were used to apply the fungicides at 30 psi and a dilution rate of 5 gal per 1000 sq ft.

The day before a spray was to be made, the fungicide treatments were weighed out at the ISU Curtiss Farm plant pathology lab south of the ISU campus. The treatments were put into 2- liter bottles. Only about ½ inch of water was added to make a slurry. The rest of the water would not be added until right before the sprays, so that the chemical reaction would occur during the spray and not the day before, when measuring took place. On spraying days the weighed samples, in a slurry form, were transported to both spray locations and filled with the appropriate amount of water. After the bottles were filled with 1.5 liters water, the treatments were immediately driven to the plots and then sprayed.

Marked stakes were placed at every sub-plot according to a map that indicated the location of every spray treatment. These stakes would be placed in the middle of every sub-plot and then pulled out after the spraying had finished.

Tyvek suits and dual-cartridge, full-face respirator masks, with the appropriate filter necessary for pesticides, were worn for protection during sprays. During a spray date all walking took place on the borders of the sub-plots. This prevented fungicide treatments spreading to sub-plots with different treatments which, if it had occurred, would have made the data unreliable.

The treatments were evenly coated at a consistent rate of application speed, moving up and down each sub-plot. The person spraying would spray one sub-plot at a time by going north and south, and then going in an east-west direction, so the spray occurred from two directions, thus fully and evenly coating a sub-plot.

In my next and final blog I will discuss the results of the experiment as well as the impact of natural events that plagued the experiment over the course of the summer.

Nails are placed appropriately on the outside perimeter of the total plot. The nails held the string tightly in place so that the corners in the inside not measured out or marked held by nails can be seen and marked with spray paint. A single continual piece of string was used to mark out the entire plot

One of the last of the inside corners, not supported by nails but now visible because of the string, is being sprayed.

Filling the backpack sprayer with a fungicide treatment that had been weighed out the day before in our Curtiss laboratory and then transported (dry) to the location in a 2 liter bottle and then filled with 1.5 liters water right before the spray.

Applying the fungicide treatment by backpack sprayer on previously marked out 5-ft x 4-ft plots at the WOI green.