Dollar Spot and Black Cutworms

Over the last three to four weeks I have received pictures from Neric Smith at Indian Hills CC (seen below), and also noticed dollar spot on several creeping bentgrass golf course tees/fairways across the state. Dollar spot is caused by the fungal pathogen Sclerotinia homoeocarpa. Generally, dollar spot develops when dew persists on the plant for greater than 8 hours. It is less dependent on temperature, and can develop over a wide range of temperatures (55-80°F). Turf deficient in nitrogen is the most likely situation where signs of dollar spot will occur. The disease gets its name from the silver-dollar-sized blighted areas that appear on closely mown creeping bentgrass. In Kentucky bluegrass and higher cut turf, the blighted area is about the size of a softball. Upon further examination of the turf affected by this disease, you will see an hour-glass shaped lesion in the middle of the leaf blade. The lesion is tan in the middle, surrounded by brown to orange halos on each side.

Active dollar spot infections produce a cottony white mycelium mass that is often evident on the turf during the early morning hours, not to be confused with spider webs. When viewed under a microscope the mycelium will exhibit y-shaped branching and the presence of septum (crosswalls). Pythium also produces this cottony white mass of mycelium but does not contain septum.

There are many ways to control dollar spot. The most important management technique is to increase N fertility in situations where N is found to be deficient. In addition to adding nitrogen; moderating thatch, removing dew, and preventing drought stress will help prevent the occurrence of dollar spot. The risk with many site-specific inhibitors is the development of dollar spot resistance. To prevent fungicide resistance use a rotation of chemicals and avoid repetitive use.  

The two pictures below were taken by Neric at Indian Hills.

 Cutworms:

The black cutworm is the most widely distributed cutworm that attacks turf in the United States. Cutworms do not overwinter in Iowa, but are brought up by winds from the south. Once they are established in the spring, they can undergo several life cycles before dying out in the fall. The adult is a dark-colored moth that is often observed fluttering around lights in the summer months. 

Cutworms, as the ones seen below, are commonly found in open aerification holes on golf course greens. A close look at the surface will reveal a lot of feeding damage around the holes.  They are often empty because of the feeding of birds. Cutworms are surface feeders and can easily be controlled with insecticides, the most common of these being Sevin (Carbaryl). While the larvae mainly emerge at night to feed, some may be seen on the putting surface during the day time, as was the case with the pictures below that was seen at Cedar Pointe in Boone a few weeks ago. 

 

 

 

NEMATODES ON BENTGRASS IN IOWA

Nick Christians

nchris@iastate.edu

June 30, 2014

Ryan Adams

rsadams@iastate.edu

Nematodes on turf is a problem that we usually don’t worry about in Iowa.  This is generally considered to be due to our cold winters that keep the population of this pest in check.  That’s why it is such a surprise to find them in numbers sufficient to cause damage after one of the coldest winters in years.

A few weeks ago, Ryan looked at some damage on Penncross creeping bentgrass (Agrostis stolonifera) greens at Westwood municipal golf course in Newton, Ia.  The symptoms looked like the patch disease Take All, caused by the fungi (Gaeumannomyces graminis).  Further tests at the Iowa State University Plant and Insect Diagnostic Clinic showed high numbers of lance (146 nematodes/100 cubic centifmeters cc) and stunt(144/ nematodes/100 cc) and some runner hyphae in the roots of the Gaeumannomyces.  It appeared that the nematodes may have weakened the turf and allowed the fungi to infest the plants, although we don’t know that for sure.

When symptoms of Take All Patch showed up on one of our research greens at Iowa State last week, we submitted samples to the Plant and Insect Diagnostic Clinic.  We didn’t expect nematodes because the damage is so rare here, but it turned out that we had 762 ring nematodes/100 cc and again this was found in association with Gaeumannomyces runner hyphae in the roots.  This is a sand-based green established with A-4 creeping bentgrass.  The damage appeared during an extremely wet period when the sand was nearly saturated.

A check of the internet for threshold levels of these nematodes shows a lot of variation around the country.  However, the specialists at the Clinic, feels that these levels are high enough to cause damage to creeping bentgrass in Iowa.

We plan to follow up with a field study on the area that will include both nematode and Take All control products in separate plots and in combinations.  We will keep you posted over the summer on what is happening.

If any of you suspect that you have this problem, let us know and submit a sample to the Clinic.  Their web site is http://www.ent.iastate.edu/pidc/.

Symptoms on green at Westwood municipal golf.

Ring nematode under microscope at the Plant and Insect Diagnostic Clinic.

Ring nematodes in the samples that we submitted to the lab.

 

SPORTS TURF PAINT PROJECT AT IOWA STATE-2014

Nick Christians
June 6, 2014
nchris@iastate.edu

Josh Lenz
jel007@iastate.edu

Josh Lenz is a new graduate student who is working on a masters of horticulture at Iowa State University.  He is doing the non-thesis option and will complete a creative component.  He works full time with the athletic department.

Josh will be looking at chemical and physical changes in the soil of sand-based sports fields subjected to repeated painting.

His treatments include:

1. Untreated control
2. Aerosol paint
3.  Acrylic paint 1:1 with water
4. Acrylic paint 2:1 with water (two part water:1 part paint)
5. Acrylic paint 4:1 with water

He will be painting the plots weekly through the season.  His measurements will include cation exchange capacity, nutrient holding capacity, water infiltration rates, bulk density and a variety of other physical soil parameters.  The study will go on for two years.

Responsible Phosphorus Use in Iowa

Phosphorus (P) is an essential macronutrient that all plants need in relatively large quantities. The amount of P fertilizer needed by turfgrass is usually significantly less than nitrogen or potassium. However, P is particularly important during early grass seedling growth and development stages.  Phosphorus plays a role in establishment, rooting, maturation, growth, and reproduction of plants. Plants can extract the relatively immobile soil P as dihydrogen phosphate (H₂PO₄^-) or hydrogen phosphate (HPO4^-2). The terms available phosphate, available phosphorus, available phosphoric acid, and P₂O₅ may be used to refer to phosphorus fertilization.

While P is an important nutrient for grasses and other plants, it is also a vital nutrient for algae and weeds in our lake systems. Phosphorus is usually the least abundant nutrient in freshwater lakes, and is often a limiting factor for the growth of algae and weeds. Lake enrichment of P can cause undesirable algal blooms and increased aquatic weed pressure, a process termed eutrophication. A result of eutrophication is an environment unsuitable for many fish and wildlife inhabitants. 

Turfgrass P deficiencies are usually first recognized by stunted growth and reduced seedling vigor. It is unusual to see a P deficiency in a mature plant. In addition to the reduced growth, leaf blades can turn a purple to reddish color. The turf stand will begin to decline in quality, if the deficiency is not addressed.

Most soils in Iowa contain adequate amounts of phosphorus and no additional phosphorus should be used in a fertilizer program unless indicated by a low soil test. A 1.0 lb. of P₂0₅ per 1000sq. ft. is permitted for establishment purposes; however, it is still strongly recommended that this application follow a low soil phosphorus determination.

Recent regulations in Minnesota and Wisconsin restrict residential landscapes phosphorus applications in an effort to minimize environmental threats. While there are no phosphorus restrictions in Iowa, phosphorus should only be applied when a soil test has indicated a need for additional amounts. The Iowa Professional Lawn Care Association (IPLCA) has placed a self-enforced restriction on the use of P fertilizers on lawns surrounding lakes and other waterways. They will use P containing fertilizers in these areas only at the time of establishment. They are also careful to remove all fertilizer from hard surfaces to prevent movement into sanitary sewer systems.

The entire extension publication is attached in pdf form.  To download the publication, click on the following link Phosphorus Publication.   

or use the following address:   

https://drive.google.com/file/d/0BzSKKI3Akgy_NEpZUGFDZmRrb0U/edit?usp=sharing

 

WILL TENACITY (MESOTRIONE) KILL QUACKGRASS?

Nick Christians
May 27, 2014
nchris@iastate.edu

Quackgrass (Elymus repens) is the hardest turf weed to control that I know of.  You can identify it by the long clasping auricles on its collar (Fig. 1) and by its extensive rhizome system (Fig. 2).  I get the question occasionally whether the new herbicide Tenacity (mesotrione) will selectively control this species.  The answer is “no”. 

Figure 1. Auricles

 Figure 2.  Rhizomes

We just treated the Kentucky bluegrass (Poa pratensis) turf at the research station shown in Figure 3.  The result is that the quackgrass turns white, as can be seen in the picture.  That always gets peoples hopes up, including mine when I first started working with this product.  Unfortunately, the quackgrass always recovers and comes back as bad as ever.  Repeat applications do not work either.  I tried for 4 seasons to kill patches in my own lawn, hoping that my tenacious applications of Tenacity would kill it.  I lost, and the quackgrass was not even reduced in severity by my repeated applications.

 

Figure 3. Quackgrass turned white by Tenacity.

The only way to control it remains non-selective applications of Roundup (glyphosate).  The rhizomes are very hard to kill and repeated applications of Roundup will be necessary.  If you have this problem and want to get rid of the quackgrass, start now in May by killing the infested areas.  Then repeat apply every time the quackgrass comes back from rhizomes.  You should set a goal of reseeding in mid-August.  

Even a better solution would be to sod over the dead areas.  The rhizomes have a harder time emerging through sod than they do into a newly seeded area.