Dollar Spot Disease 2010, Tim Sibicky, CDGA Turfgrass Research Manager

Warmer temperatures this week have provided suitable environmental conditions for dollar spot (Sclerotinia homoeoecarpa) development on fairways. We are now beginning to see a lateseason 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

Weeds at the Hong Kong Golf Club

Recently I have been getting e-mails from friends and family back in Iowa telling me about all the weed pressure this season from the wet weather conditions. Their messages got me thinking about some of the weeds around here in Hong Kong and I thought it would be interesting to share about three different types of weeds that are an ongoing battle for us here at the Hong Kong Golf Club.

Goosgrass Eleusine indica
Goosegrass is a summer annual grass, which grows as a perennial here in our subtropical climate. Goosegrass pressure is intense on nearly all parts of the course and grows very well in compacted and high traffic areas. Recently, a pre-emergent herbicide plan has been implemented using Barricade and we have had great success. By using this pre-emerge program in the fairways, roughs and all other major play areas, we have saved a massive number of man-hours that were devoted to hand pulling weeds. We still have a crew of who spends a majority of their day walking the fairways with a weed removing tool and a trash bag trying to control the Goosegrass. At the end of the day most of the managers have filled up the back of their carts from pulling Goosegrass on their courses whenever they see a troublesome clump trying to take over.

Water Hyacinth Eichhornia crassipes
Water Hyacinth is a water dwelling weed that is incredibly invasive and can destroy the make up of a pond or lake. It quickly covers the entire top of a body of water, cutting out sunlight to lower levels, and sucks all the oxygen out. There was an article in the August edition of Golf Course Management (pg 40) about a new insect that they believe will help control populations of Water Hyacinth. Unfortunately, the insect is just being released in Florida and I do not know if it will ever be made useful here in South East Asia. Our current control method is again, manual removal. Every few months our landscape team will go in and remove all the Water Hyacinth from this pond. Unfortunately, if you leave just one leaf, it will be completely covered again. We are keeping our fingers crossed it does not invade other ponds on the course.




“Creeper” Mikania micrantha
Chinese Creeper, or more commonly known just as “Creeper” is a weed that has most of Hong Kong in its grips, literally. Creeper is a perennial weed that quickly grows and overtakes trees and all other vegetation. It smothers them from the light and eventually kills them. This vine can be seen taking over forests in the mountains and if anything sits for too long, creeper will eventually overtake it. Our arboriculture team regularly removes the vine from our tree lines here at the golf course. They do a great job keeping it from overtaking our natural areas, but it is a never-ending job. There are some chemical controls for it, but it is easiest and safest to just remove by hand and to try and keep populations at a minimum so it doesn’t get out of control.

Damian Richardson
Hong Kong Golf Club

Improving Accuracy of Disease Rating for Dollar Spot on Turf

Nick Christians
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.

Methods for Raising Sprinkler Heads

John Newton, CGCS, Veenker Memorial Golf Course is interested if anyone has a good method for raising sprinkler heads. If anyone has an alternative procedure beyond the traditional method of digging the head down to the swing joint, please share your thoughts by leaving a comment at the end of this post.

John’s question immediately made me think of the LeveLift system. I first learned of the LeveLift device during a presentation from one of our students who had interned at a golf course that had one. It’s definitely work checking out If you have never seen it before. The LeveLift was developed by a former golf course Superintendent. The device uses the water pressure from the irrigation system to lift the sprinkler head into a level position. You can see a video of the LeveLift system in action by clicking here.

Marcus Jones
Graduate Research Assistant

CREEPING BELLFLOWER IN AMES LAWN

Nick Christians
Sept. 22, 2010

Here is the unusual weed of the week. It came from an Ames lawn. It looks like Ground Ivy (creeping charlie) except it does not have a square stem and does not have the mint odor. Also, it is spreading by underground rootstalks and not above ground runners.

It is Creeping Bellflower (Campanula rapunculoides). It is an escaped ornamental that has become an invasive weed. It has a blue, bell-shaped flower at some times of year, but in mowed conditions may go most of the season without a flower.

It is hard to kill. It is resistant to 2,4-D and many of the other common lawn herbicides. You will need something with Dicamba in it and it will still likely take several applications. Luckily, it is rare in Iowa.

Fall is in the Air

A change of seasons is upon us.  The leaves are beginning to drop from some trees and the day lengths are getting noticeably shorter.  September has brought with it cooler day and nighttime temperatures and average 4-inch soil temperatures even dipped into the high 50’s yesterday.  These favorable environmental conditions have allowed existing turf the chance to recover and newly sown seed the opportunity to germinate and begin to cover.

The fall is also a great time to clean up unwanted creeping bentgrass.  Because of all the rainfall and submerged conditions we experienced during the summer months, creeping bentgrass had an opportunity to gain a competitive advantage and may have spread into areas where it wasn’t present before.  Luckily, creeping bentgrass can be controlled with Tenacity herbicide.

Tenacity is a systemic herbicide with pre- and post-emergence activity on many grass and broadleaf weeds.  Tenacity is also capable of selectively removing creeping bentgrass from Kentucky bluegrass, perennial ryegrass, tall and fine fescue.  Multiple applications of Tenacity are required for complete control of creeping bentgrass.  

Tenacity works by inhibiting HPPD enzymes which aid in the synthesis of carotenoids.  Carotenoids help to protect the plant from excess light energy received from the sun.  Without these protective carotenoids, the excess energy causes new growth to turn "bleach" or turn white and eventually kills susceptible plants.

I have done quite a bit of work with Tenacity.  Below are some pictures from my research and from golf courses who have used the product. 

 

Plot of turf adjacent to a creeping bentgrass putting green after recieveing one application of Tenacity herbicide.  The bentgrass (susceptible) turns white, while the Kentucky bluegrass remains unaffected.

Here, Tenacity was applied to an intermediate cut of Kentucky bluegrass to clean up creeping bentgrass that had invaded from the fairway.  Bleaching of the bentgrass appears after just 1 application.

Applying tenacity next to monostands of creeping bentgrass needs to be done with caution.  Here, spray drift from the adjacent treated turf caused bleaching symptoms on a creeping bentgrass green.  Bentgrass will not be completely controlled after one application but the "bleaching" symptoms can be unsightly in the wrong spot.

Multiple applications of Tenacity are needed for complete control of bentgrass.  Here, three applications have killed the majority of creeping bentgrass in a stand of Kentucky bluegrass. 

For more information about Tenacity herbicide and its various uses visit the Syngenta Tenacity page.

Marcus Jones
Graduate Research Assistant

Iowa Based Internships

Thinking back to when I was an undergraduate, I remember what a great learning experience my internships were.  I could finally start to apply some of the information I had learned in the classroom and I was able to communicate and interact with field experts on a daily basis.  Similarly, from my time spent in industry, I understand how staffing reliable, enthusiastic workers can benefit the day to day operations of any facility.  The bottom line is that internships can be beneficial to both the student and the facility alike.

Some of you may have had an intern from ISU at your facility in the past and others may be curious about employing an intern in the future.  Our department has approximately 50 turfgrass students who will be looking for internship opportunities this coming summer in golf, sports, and lawn and landscape settings. 

These potential interns (along with their resumes) will be available for an informal meet and greet at our upcoming Horticulture Career Night.  The event will be held on Monday, October 18 at Reiman Garden’s just south of the ISU campus.  The event will begin at 5:30 pm and food and beverages will be provided at no charge.  Consider coming to this event to recruit potential interns.  Those planning on attending need to RSVP to Marcus Jones at mjones99@iastate.edu.  

Marcus Jones

Graduate Research Assistant