Search results

Holy Mycelium!

July 8, 2011

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

Category: 

2010 Creeping Bentgrass-Dollar Spot Study

June 1, 2011

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).

 

Table 1. Varieties of creeping bentgrass in commercial bentgrass demonstration trial.

Entry No.

Fairway Height Varieties

Green Height Varieties

1

L-93

L-93

2

T-1

T-1

3

Alpha

Alpha

4

Putter

Putter

5

Southshore

Southshore

6

Kingpin

Kingpin

7

Crenshaw

Crenshaw

8

Imperial

Imperial

9

Century

Century

10

Penncross

Penncross

11

A-4

A-4

12

Crystal bluelinks

Crystal bluelinks

13

Alister

Penn A-1

14

Pennlinks II

Penn G-6

15

007

007

16

MacKenzie

MacKenzie

17

Tyee

Tyee

18

SR 1150

SR 1150

19

Memorial

Memorial

20

Independence

Independence

21

Declaration

Declaration

22

LS - 44

LS - 44

23

Bengal

Bengal

24

Penn G-6

Alister

 

 

 

Table 2. Quality ratings for green-height and fairway-height cultivars of the creeping bentgrass demonstration trial.

 

Quality

 

Quality

Cultivars (green)

2010

Cultivars (fairway)

2010

L-93

5.9β

L-93

6.4β

T-1

5.4

T-1

6.2

Alpha

5.4

Alpha

6.6

Putter

5.8

Putter

6.2

Southshore

5.8

Southshore

6.0

Kingpin

5.7

Kingpin

6.3

Crenshaw

6.2

Crenshaw

5.9

Imperial

5.6

Imperial

6.3

Century

5.5

Century

5.9

Penncross

6.2

Penncross

6.0

A-4

5.6

A-4

6.0

Crystal bluelinks

6.1

Crystal bluelinks

6.4

Penn A-1

5.9

Alister

6.1

Penn G-6

6.1

Pennlinks II

6.1

007

5.1

007

6.2

MacKenzie

5.3

MacKenzie

6.2

Tyee

5.0

Tyee

6.0

SR 1150

4.7

SR 1150

5.8

Memorial

6.3

Memorial

6.5

Independence

5.1

Independence

5.6

Declaration

5.0

Declaration

5.7

LS-44

6.2

LS-44

6.5

Bengal

5.7

Bengal

6.4

Alister

4.2

Penn G-6

6.4

LSD(0.05)

0.9

LSD(0.05)

0.6

Quality data rated on a scale of 9-1, with 9 = excellent turf; 1 = poorest quality; 6 = minimally acceptable.

Ratings are the average of three replications, averaged over the months of June to October.

Ratings observed only on fungicide-treated side of plot area.

βRatings are the average of three replications, averaged over the months of May to October.

 

 

Category: 

PATHOLOGY RESEARCH SUMMER 2010-3rd POST

December 20, 2010

Here is the 3rd post by undergraduate student Steve Johnson on his pathology project at ISU during the summer of 2010.
 

Steve Johnson, Soph. Summer Intern Blog #3

Following my last blog I will discuss the results of the experiment.

Assessments of the turf were made by my instructor Mark Gleason, Professor of Plant Pathology and Horticulture at Iowa State University. Data were recorded on 2 July, 15 July, 26 July, and 18 August at the Turfgrass Research Area of the ISU Horticulture Research Farm near Gilbert, IA, and at a green near the WOI Building on the ISU campus. Dollar spot was recorded as a percentage of the area in a 5-ft x 4-ft plot that was covered with the disease; all treatments had 4 replicate plots, arranged in a randomized complete block design. Turf quality ratings were set on a qualitative scale of 1 to 10 where 10 indicated no disease, excellent quality, and a 1 indicated very poor turf quality. Data were analyzed using the GLM procedure and SAS (statistical analysis software) with mean separations determined by Fisher’s protected LSD at P<0.05.

Weather conditions for the 2009 summer hit record highs in heat, rainfall, and humidity. Heavy rainfall caused extensive flooding in the Ames area which persisted from 11-13 August. There were no signs of phytotoxicity seen on the turf for the duration of the trial for either location. However, worth noting is that all four sub-plots for treatment 11 (a pre-mix of chlorothalonil and propiconazole) at the Hort Farm displayed a darker green coloration and sometimes slight browning on 15 and 26 July.

At the Hort Farm, dollar spot was light to moderate in disease intensity over the course of the summer. Intensity peaked in late July with a decline occurring by August. However, due to variation among subplots, most treatments did not vary significantly from the untreated control. Turf quality had similar results, with most of the treatments showing a consistent decline in the quality as the summer progressed.

However, many fungicide treatments exhibited significant difference in dollar spot severity on 2 July and 26 July. In addition, a few of the treatments maintained good quality the entire summer, indicating that that these treatments proved effective against dollar spot and preserved adequate turf visual quality despite the stressful growing conditions.

For WOI, the data were in question due to a severe outbreak of crabgrass. Creeping bentgrass at the location was overwhelmed to such a degree that WOI will not be used again for future experiments. There were two reasons for this. Golf course maintenance was inhibited due to tree damage from a storm in mid July that produced 70-mph winds, as well as severe flooding from 11-13 August. While I have made available the data in Tables, the results are questionable for WOI.

I have attached 4 Tables showing the data that were collected on check dates over the summer. Data Tables include: dollar spot % severity at the Hort Farm and WOI, as well as turf quality for the Hort Farm and WOI. On 26 July, Mark and I independently assessed % dollar spot severity at the Hort Farm. As was explained in the earlier blogs, this was to improve the reliability of the disease % ratings of dollar spot on turf by combining the impressions of two raters. The data was averaged between Mark and myself and was recorded under 26 July column for the Hort arm % dollar spot Table.

Despite the numerous and overwhelming weather issues and outburst of crabgrass at WOI, this experiment still yielded some good data concerning the effectiveness of fungicide treatments. Also valuable is the method of averaging disease ratings from multiple raters to reduce individual biases. The amount and reoccurrence of fungicide sprays are factors determined by accurate readings which can save money and resources as well as prevent over-applications of fungicides which can lead to phytotoxicity of grass blades. It is methods and good data learned from studies such as this one that can prove quite useful in telling how well established a disease is and aid owners in deciding upon a proper integrated disease management program for optimal disease prevention.






 

 

Category: 

Improving Accuracy of Disease Rating for Dollar Spot on Turf

September 27, 2010

The following is a post from a student named Steve Johnson. He is an undergraduate who was working for Dr. Mark Gleason on a pathology research project this summer. He is doing this as part of the requirement for his Hort 391 special studies course. Hopefully, this will start a trend and we will have several other posts like it this fall.

Steve Johnson, Soph. Summer Intern Blog #1

Many turfgrasses are susceptible to fungal diseases and this leads to many maintenance issues for turf practitioners.  In response to the detrimental effects of turf diseases caused by a wide assortment of fungi, a precise reading of the amount of turf infected by a disease is needed to determine the proper course of action.

In evaluating alternatives for suppressing turf diseases, its important to have a method to separate the effective treatments and the from the less effective ones.  This often requires replicated field trials, often at multiple sites, comparing each alternative in the same turfgrass stand.  But how, exactly, does one measure disease severity.

Disease severity is usually measured by some sort of visual estimation method.  In other words, you look at the turf that was treated with each respective fungicide treatment and try to visually estimate a number a represents how severe the disease symptoms appear.  This is not always accurate and may not be consistent from one rating to the next or from person to person.

As an example of this, lets consider the turf disease dollar spot, caused by the fungus Sclerotinia homeocarpa. Dollar spot is a relentless disease that is recognized by it distinctive lesions that are often the size of the a silver dollar and the lesions can grow together in severe cases.  Dollar spot is the most expensive disease to control on golf courses across much of the Midwest and Eastern United States.

In comparing dollar spot fungicide treatments to each other, how can we measure disease severity?  One way is to estimate the percentage of the plot that has turned brown due to the disease.  But one person rating the percentage of dollar spot may come up with a different number than someone else.  Others have two people rate the same plot independently of each other.  So how can we be sure that the disease ratings are consistent and reliable? 

Evaluating a way to accurately estimate dollar spot severity on greens-height creeping bentgrass was the objective of this study.  We wanted to find out how different two people would rate the same turf plots, and then average the ratings to reduce bias from individual ratings.  A trial was conducted during the summer of 2010 at the ISU Horticulture Research Station to evaluate dollar spot severity on creeping bentgrass.

The results of this study are mean to be relevant for disease severity ratings of many diseases and grasses, not just bentgrass and dollar spot.  
 

Figures

Examples of turf from the Hort farm plots infected with dollar spot.

1 and 2.

ISU Horticulture Farm turf plot marked out for the experiment. The white string was used to show where the corners of each were.  We then spray-painted the corners in order to visually locate where each plot was without the strings.  The strings were removed after all the corners had been painted so regular maintenance could continue.

WOI green located just north of Roy J. Carver Co-Lab on the northwest edge of the ISU campus.  It was marked out and prepared for the experiment in the exact same manner as the plots at the Research Station.

Category: