Postemergence Crabgrass Control

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

It seems like every year is now a crabgrass year and this year is no different.  Even though summer temperatures have been less than stressful to this point in the summer frequent rainfall has kept the turfgrass and the crabgrass growing.  The best defense against crabgrass invasion is maintaining a healthy, dense turf stand by mowing high and fertilizing throughout the season.  If postemergence crabgrass control is in your future here’s a quick herbicide primer.       

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. 

Crabgrass enjoying the summer next to a sidewalk.

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 (active ingredient (a.i.) quinclorac)), Acclaim Extra (a.i. fenoxaprop-ethyl), Tenacity (a.i. mesotrione), and Pylex (a.i. topramezone) are all effective for postemergence control.  For homeowners the primary herbicide you will find on the shelf at your favorite store for postemergence crabgrass control will contain quinclorac. 

Quinclorac provides excellent control of crabgrass at almost any growth stage (seedling or mature) and is very safe when applied to new seedings.  Quinclorac, mesotrione, and topramezone also have the added benefit of providing control of some broadleaves such as white clover and dandelion.  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.  Topramezone also provides control of goosegrass.

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. 

New Asian Earthworm on Golf Courses

Dr. David Smitley
Michigan State University

In Kentucky, Dr. Dan Potter has been studying the types of earthworms found on golf courses.  Traditionally most of the earthworms found on golf courses in North America are one of three or four species from Europe in the family Lumbricidae, mostly L. terrestris and Aprorrectodea spp.  These species tend to make mounds when the soil is saturated, especially in fall and early spring.  They do not usually cause mounding problems on sand-based greens.  In some recent survey work in Kentucky, Dr. Potter discovered an increasing frequency of a new earthworm from Asia: Amynthas hupeiensis. This is the most important earthworm problem on golf courses in Korea. A summary of his report is available at:

http://kentuckypestnews.wordpress.com/2014/04/08/invasive-earthworms-newest-threat-to-landscape-and-golf-course-turf/

At this point we do not know how widely distributed Amynthas spp. are in Michigan or other Midwestern states, although it has been reported from Illinois.  If you are seeing change in earthworm mounding activity on your golf course, and particularly if you are seeing more mounding on sand-based greens during the summer, please let me know at:  smitley@cbs.msu.edu

Ataenius and Cutworms Active on Golf Courses

Dr. David Smitley, Terry Davis, and Dr. Kevin W. Frank

Michigan State University

In the last week both Ataenius grubs (Ataenius Spretulus) and cutworms (Agrotis Ipsilon) have been observed feeding in Poa annua and creeping bentgrass putting greens.  Ataenius grubs have been found causing significant injury on Poa annua greens that have recently recovered from winterkill.  Due to the rather short root system of recovering Poa, it appears in some area the Ataenius grubs are causing injury at lower than normal thresholds.  The typical threshold for recommending a curative insecticide application is 40 grubs/ft.².   For curative insecticide applications use carbaryl or triclorfon.  These insecticides need to be applied at the full application rate and watered in with ½ inch of water following application.  Additional information on Ataenius can be found at http://msuturfinsects.net/details/_/ataenius_and_aphodius_6/

 

Ataenius grubs.

Turf easily peeled back from grub feeding.

Skunk and bird damage from feeding on grubs.

Cutworms are also active on putting greens.  Damage looks similar to an unrepaired ball mark.  Cutworms will often chew the stems of grass plants around the entrance to their tunnel, leaving a yellow ‘ball-mark’ patch.  A “disclosing solution” consisting of 1 oz of liquid detergent in 3 gal of water can be poured over suspected infestations to force the cutworms to the surface.  In approximately 3-5 min the larvae will come to the surface and will be very evident. Synthetic pyrethroid insecticides such as deltamethrin, cyfluthrin, bifenthrin, permethrin and lambda-cyhalothrin will work very well to reduce damage from cutworms. Safe alternative products include Bt (Bacillus thuringiensis) and insect parasitic nematodes. Any insecticide applied to tees, greens or fairways may need to be reapplied every two weeks during periods of maximum cutworm moth activity, because most of the insecticide residue is removed daily or every other day with the clippings.  Additional information on cutworms can be found at http://msuturfinsects.net/details/_/cutworm_10/

Black cutworm on putting green.

Creeping Bentgrass Establishment

Eric Chestnut, Thomas Green, and Dr. John N. Rogers, III

Michigan State University

Due to the recent harsh winter and new bentgrass varieties that have come into the market, a study currently underway at the Hancock Turfgrass Research Center at Michigan State University has become quite timely and relevant. Pure Distinction creeping bentgrass was seeded into a bare soil profile last August with the intent of using four factors (nitrogen fertilizer rate, mowing height, PGR use, and verticutting) to discover the fastest way to get a plot of turf capable of withstanding putting green traffic. Although the following observations are preliminary, we hope that those interested may find them useful.

Pure Distinction 5/5/14. 

As of May 29, 2014, only the nitrogen fertilization and mowing height regimens have been implemented  long enough to notice any treatment differences. The most striking contrast is between the fertilizer rates. Rates of 0.05, 0.10, and 0.15 lb N/1000 ft² are sprayed (initiated Sept. 2013) weekly. The photographs below reveal that the plots receiving 0.10 lb N/1000 ft² and 0.15 lb N/1000 ft² of fertilizer are much farther along than the plots receiving 0.05 lb N per week. The differences between the two higher rates are currently harder to differentiate, but the highest (0.15 lb N/1000 ft²) rate did seem to grow in significantly faster initially than either of the other two rates. The warm air and soil temperatures during the past couple of weeks have given most of the 0.10 lb N/1000 ft² plots a chance to catch up to the highest rate, but the lowest rate plots still have significantly less coverage than the others.

Pure Distinction 5/25/14. Darker green areas are 0.10 & 0.15 lb N/1000 ft² rates and thin areas are the 0.05 lb N/1000 ft² rate.

Mowing was initiated last fall and resumed this year on April 30, 2014 yielded minimal clippings until the second week in May due to cold soil and air temperatures. Half of the plots were originally being mowed at 0.200” and the other half at 0.150”, with each height being reduced by 0.05” each week until a height of 0.125” is reached. Mowing heights are currently at 0.190” and 0.140”. Plots being mowed at the lower height are growing in more densely than areas at the higher cut, even though they look similar from a standing distance due to longer, more lateral growing leaves on the higher cut turf (see Figures 4-7).

Mowing Height Differences. 5/29/14.  Plot on the right (above the 1) is mowed at 0.140” and the plot on the left (above the 2) is mowed at 0.190”. Both plots fertilized at 0.150 lb N/10000 ft². They look very similar from above, but upon closer inspection the lower mowing height (the plot on the right) has more leaf density than the higher height (plot on the left).

Mowing height 0.190”. 5/30/14. Notice there are quite a few areas where the leaves are sprawling outward instead of standing up.

          

Mowing height 0.140” 5/30/14. When compared to the higher mowing cuts the grass blades are more upright and less sprawling.

The verticutting regimen was initiated on May 28, 2014. At the time this post was written, the cutting was too new to see any differences between plots. The PGR applications will began  the week of June 1, 2014.

Multiple Factor Photo. 5/26/14. Plots below the number 2’s are mowed at 0.190” and plots below the number 1 (second from the right) are mowed at 0.140”. Fertilizer rates are as follows from left to right: 0.05 lb N/1000 ft², 0.05 lb N/1000 ft², 0.15 lb N/1000 ft², 0.10 lb N/1000 ft².