Bacterial Etiolation and Decline

Paul R. Giordano and Dr. J.M. Vargas, Jr.

Michigan State University

Early characterization of the new disease named bacterial etiolation and decline, and the pathogen that causes it - Acidovorax avenae subsp. avenae (for the sake of my sanity, I will call it Acidovorax from here on) have been well documented .  Much of the controversy surrounding the disease comes from its unpredictable and inconsistent symptomology in nature (on the golf course).  A key constraint in the progress of the research has been the inability to consistently reproduce the etiolation or abnormal elongation symptoms.  Golf courses afflicted with this disease TYPICALLY show symptoms of yellowing and elongation as summer temperatures begin to rise into the 80’s. As temperatures progress into the 90’s and humidity is high, these chlorotic, overgrown areas begin to thin, and eventually die.  Early research on creeping bentgrass with Acidovorax showed severe damage and blight; however, the etiolation symptom was not reliably reproduced.  This posed a problem, particularly among turfgrass pathologists who have tirelessly argued over whether this is a “true” disease or not.

Bacterial etiolation on plots at HTRC.

Trial and error and continued research efforts have (finally) given rise to reliable induction of etiolation symptoms through inoculation of the bacteria into roots of creeping bentgrass plants (data currently submitted for publication). This confirms the association of Acidovorax with etiolation in a controlled environment, however, unless it can be done in a field setting, there will always be questions related to the true cause and nature of the disease.

Bacterial streaming from a turfgrass leaf.

Over the past 4 years, field research on bacterial etiolation at numerous sites around the country has taken place. Initial trials were set up at Quail Hollow in Charlotte, North Carolina, and subsequent research has been conducted on golf courses in Dayton, OH, Toledo, OH and, of course, East Lansing, MI.  The studies on golf courses have provided some interesting results, however, the disease symptoms are often sporadic, and conducting research on in-play, high-end putting greens has many inherent limitations. This is why the Hancock Turfgrass Research Center is an ideal proving ground for disease research: we have complete control of the management practices and freedom to encourage disease in a very deliberate manner. 

Unfortunately, achieving consistent etoliation the past three years have been relatively unsuccessful. Last summer we observed short-lived etiolation during a hot spell in mid-July, but symptoms were inconsistent and not uniform throughout the study.  Since Ph.D. students are (ideally) around for about 4 years...the clock is ticking for some quality field results.  Channeling this desperation, we devised a strategy this past winter to finally get bacterial etiolation on our research plots. This plan incorporated all of the knowledge we have gained from the project thus far, as well as some anecdotal observations we have made over the years…Lo, and behold, it worked!     

Clever thinking by Dr. Vargas suggested we bring in entirely new creeping bentgrass sod to the area. This notion was based on observations at golf courses with Acidovorax problems. Usually the areas that were plugged or sodded with nursery creeping bentgrass showed symptoms within a few days of transplanting.  The new sod was established in mid May of this year, and since then, the management strategy has been aggressive: double mowing, rolling, heavy topdressing, and low fertility, all of which have shown to be common factors on golf courses battling bacterial etiolation.  Symptoms of etiolation appeared last week, after a brief, but much appreciated stint of warm, humid weather (plant pathologists get inexplicably excited during disease weather). Yellow, elongated plants were full of Acidovorax, as determined by microscopic observations of bacterial streaming.  Several treatments are under investigation on plots this summer, which hopefully yield informative results related to symptom suppression or alleviation.

Sodding a new green at the HTRC.

No promises are being made, but this is shaping up to be a banner year for bacterial etiolation at MSU’s Turfgrass Field Day in August.  Stay tuned for more on this emerging disease and the exciting and pioneering research we are doing at Michigan State. 

Postemergence Crabgrass Control in Turf

Dr. Kevin W. Frank & Aaron Hathaway
Michigan State University

The recent warm temperatures have pushed crabgrass to the surface in many areas.  Crabgrass I’ve observed has progressed quickly from emergence to 3-4 leaf stage or beyond quickly.  Thin turf areas, low cut turf (such as golf course fairways) or turf near sidewalks, driveways, and roadsides, where temperatures are warmer are usually the first place to look to find crabgrass.   The best defense against crabgrass invasion is maintaining a healthy, dense turf stand by mowing high and fertilizing.  Crabgrass is a warm season annual that thrives at high temperatures.  If postemergence crabgrass control is in your future here’s a herbicide primer.       

Crabgrass infesting turf.

Postemergence Control

Postemergence control is generally more effective when crabgrass is younger before it has tillered.  As crabgrass matures, postemergence control becomes more challenging and multiple applications spaced 2-3 weeks apart are necessary to achieve control. 

MSMA is no longer available for selective grassy weed control in lawns/commercial turf.   MSMA can be used on golf courses and sod farms.  There are several options for controlling crabgrass in cool season turf: Drive (a.i. quinclorac), Acclaim Extra (a.i. fenoxaprop-ethyl), and Tenacity (a.i. mesotrione) are all effective for postemergence control.

Quinclorac provides excellent control of crabgrass at almost any growth stage (seedling or gorilla-sized) and is very safe when applied to new seedings.  Quinclorac has the added benefit of enhancing broadleaf herbicide activity when tankmixed with other broadleaf specific herbicides.  Quinclorac also is excellent for control of some broadleaves (white clover and dandelion) on its own. Fenoxaprop-ethyl is generally not as effective on larger or more mature crabgrass as quinclorac, but can provide excellent control of other grassy weeds, such as goosegrass, that are not effectively controlled by quinclorac.  Mesotrione is also very effective for postemergence crabgrass control. 

Controlling Crabgrass at Establishment

For those that are considering establishing new turfgrass this summer, controlling crabgrass can be the difference between success and starting over again in the fall.  Tupersan (a.i. siduron) is the traditional stand-by for controlling weeds during seeded turfgrass establishment.  Newer to the scene is Tenacity which can also be used safely at the time of seeding. 

Always read, understand, and follow the label directions. Mention or exclusion of specific products does not represent an endorsement or condemnation of any product by Michigan State University. 

Red Thread in Turf

Dr. Kevin W. Frank & Dr. Joe Vargas, Jr.
Michigan State University

The frequent rains this year have not only resulted in mowing challenges but have also resulted in some turf areas in need of nutrition.  Not surprisingly reports of red thread (Laetisaria fuciformison) on lawns and landscape turf areas have been frequent for several weeks now.  It seems that every year we observe red thread on lawns or golf course roughs and often the outbreak follows the seed head production period when the plant is probably looking for a little extra nutrition.  The common lawn mix turfgrasses Kentucky bluegrass, perennial ryegrass, and fine fescue are all susceptible, with perennial ryegrass being particularly susceptible.   Red thread is typically active during wet, moist periods when temperatures range from 55 to about 80 degrees. Red thread can be identified by the pinkish-red strands (stroma) that extend from the leaf blade tip.  The pinkish-red strands are easily observed in the morning when the turf is still moist from dew.  The areas infected by red thread will die and the turf may appear wilted.  Red thread can be mistaken for dollar spot in turf as the patchy type kill is very similar.  This is one of those diseases you need to get on your hands and knees to check out to make sure you know that it is red thread.  Fungicide applications are usually not necessary in dealing with red thread; a fertilizer application will often help the turf outgrow the damage.

Red Thread in Kentucky bluegrass

Red Thread with pink stroma visible.

Yellow Nutsedge in Turf

Kevin W. Frank
Assoc. Professor & Extension Turf Specialist

While mowing my own patch of green last evening I noticed that one of my peskiest weeds has reappeared, yellow nutsedge (Cyperus esculentus).  I always find it helpful to look back through my records to see what I’ve written about in past years and what I perceived to be big problems.  After perusing my files I found references to nutsedge being particularly troublesome in 2000 and 2004.  Without pouring over historical weather data, both of these summers were recorded in my files as being cool, wet summers, just like the beginning of this season.  Only time will tell if 2013 becomes another ‘nutsedge year’.       

Yellow nutsedge is often called nutgrass or swampgrass.  It’s not a broadleaf, it’s not a grass, it’s a sedge and is easily identified by the triangular shape of the stem.  If you roll the stem between your fingers you should be able to feel the triangular shape of the stem.  Other distinguishing characteristics of yellow nutsedge include leaves that are light green to yellowish in color and waxy or slick to the touch.  Yellow nutsedge grows rapidly and the leaves are often seen several inches above the turfgrass canopy, similar to what is often seen with quackgrass.  Nutsedge produces tubers or nutlets underground that really make controlling this weed difficult.  These tubers can remain dormant in the soil for several years and sprout new plants when moisture becomes available.

Yellow nutsedge in a Kentucky bluegrass lawn.

 What are the options for controlling nutsedge in turf?  The first step, which has been challenging this year, is to keep up on your mowing schedule to prevent seed production, even though by most accounts seed is unlikely to germinate.  Hand weeding may be effective in a mulch bed but in turfgrass is a very difficult task. If you don’t get the underground tuber when you pull, you’ll be pulling again shortly. For the serious infestations a herbicide application may be necessary. 

Control options for the homeowner are somewhat limited, look for herbicides with the active ingredients sulfentrazone or halosulfuron.  Control options for professional applicators are more diverse.  In addition to the standby’s sulfentrazone and halosulfuron, mesotrione and a new herbicide Celero with the active ingredient idosulfuron provide control.  For serious infestations repeat applications over several years will likely be required to achieve complete control, remember all those nutlets resting under the surface waiting to grow new plants next year. 

Always read, understand, and follow the label directions. Mention or exclusion of specific products does not represent an endorsement or condemnation of any product by Michigan State University.  

Turf Tips during Wet, Cool Weather

Kevin W. Frank
Assoc. Professor & Extension Turf Specialist

At least to this point in the year the weather of 2013 couldn’t be any different than 2012.  The season of 2012 was characterized by high temperatures and extended dry conditions.  Now that we’re about mid-June, nary an air conditioner has been fired up and most turf managers are just hoping for a couple days of dry weather.  Although precipitation is always somewhat scattered and variable from location to location, since Sunday night many locations have received between 1 to 3 inches of rain, and this wasn’t following a dry spell.  What challenges do the cool weather and abundant precipitation present for managing turf?

1.  The turf just won’t quit growing.  This isn’t necessarily a bad thing but it sure does make it difficult to keep up with mowing.  All of the turfgrasses we grow in Michigan are cool-season which means this weather is absolutely optimal for their growth.  We often get questions about mowing turf when it’s wet and whether or not this is detrimental to the turf.  Generally, mowing turf when it is wet is not a problem for the turf but may be a problem for your mower.  Some mowers may start to clog up when mowing wet turf, especially if the turf is a little taller than you’d like.  Besides issues with the mower clogging, mowing wet turf will dull the mower blade quicker than if you are always mowing dry turf.  In addition to mower issues, and certainly more important in the long run is the potential to compact the soil or cause physical damage to the turf when turning a mower when the soil is wet or saturated.  Unfortunately at some point you’re probably not going to have any choice and you’re going to need to mow even if the soil is wet.  Just keep this in mind and make sure to schedule a core aeration at some point in the future to alleviate any compaction you may have created by mowing on wet soils.  This of course is of greater concern for those using riding mowers than for a homeowner using a push behind walk mower. 

Surge growth has made keeping up with mowing tough.

2. Saturated soils result in declining turf quality.  Poorly drained turf areas where water has been sitting for several days may be yellow or brown.  There are several reasons for the discoloration but one of the main reasons is impairment of the root system.  It doesn’t take long once the soil is saturated for soil oxygen levels to decline and root hairs to begin to die.  As the turf’s root system becomes impaired nutrient extraction and water uptake will be limited.

3. Turfgrass may be slow to respond to fertilizer applications.  Fertilizers that release nitrogen based on temperature (natural organics, methylene urea, poly-coated urea) have been slower to produce turfgrass responses this year due to the cool temperatures.  The best advice with respect to a lack of observed response is to be patient.  Don’t make the mistake of thinking the fertilizer application didn’t work and make another fertilizer application, given some time and warmer temperatures you’d then end up with essentially a double fertilizer application all releasing at the same time.

4. Turfgrass may need additional fertilizer as we move through the summer.  At first this may seem completely contradictory to #3 above but keep in mind that with the cool temperatures and abundant rain the turf has been growing like crazy and burning through fertilizer applications.  The important consideration is to understand what fertilizer you applied (#3 above) and adjust product and application frequency as needed.  As many turf managers already do, let the turf tell you when it’s hungry and don’t be afraid to feed it.  A dense, healthy turfgrass stand is more resistant to all types of pest pressure.