Hurry Up and Wait. Now Go!

At the beginning of March we were potentially a week or two away from annual bluegrass seedhead emergence thanks to an extremely warm February. Cooler temperatures prevailed and significant snowfall across much of the Northeast brought soil temperatures down and put the brakes on annual bluegrass development for a few weeks. It’s now the beginning of April and we are very close to annual bluegrass seedhead emergence on putting greens in central New Jersey. Parts of northern New Jersey appear to be about a week behind the New Brunswick area.  If you haven’t already applied ethephon (i.e., Proxy, Ethephon 2 SL, Oskie) for seedhead suppression, this week might be ideal (see previous post for more information) for most courses in New Jersey.

Warmer temperatures this week will likely bring average 24-hour soil temperatures (one inch depth) into the 50s and turf will begin to grow more rapidly. Emergence of summer annual weeds is not far away. I first noticed prostrate knotweed emergence in mid February. These early germinating plants survived the winter weather and will continue to develop this week.

Prostrate knotweed seedlings

Note that knotweed seedlings will have two seed leaves and crabgrass will have only one.

Prostrate knotweed seedling with two seed leaves

 

Smooth crabgrass seedling with one seed leaf

I have not observed crabgrass emergence, even on south-facing slopes. I spent the latter part of last week in Washington D.C. and could not find any crabgrass along sidewalks and bare areas there either.

Crabgrass emerging with one seed leaf (in a previous year)

Depending on your location, forsythia may or may not be a reliable phenological indicator for crabgrass germination this year. In a normal year, pre-emergent herbicides (except for dithiopyr (Dimension), which can control crabgrass up to the pre-tiller stage) should be applied when forsythia is in full bloom because crabgrass germination will occur shortly thereafter. However, extremely cold temperatures killed or injured many forsythia flowers in central Jersey and areas south.

In northern New Jersey I’ve observed forsythia plants still in the bud stage and in this case they are likely to be effective indicators. Especially this year, it is important to use multiple forsythia plants because the bloom timing is affected by location among other factors. Plants that bloomed early were injured by the winter weather, but others were unaffected as this photo from @samcamuso demonstrates.

Soil temperature at a 1-inch depth has been reported as a reliable indicator of crabgrass germination assuming soil moisture is adequate. In a three-year study, Fidanza et al. (1996) found that crabgrass began to emerge when the soil temperature at a 1-inch depth averaged 57 to 63 degrees during a 7-day period. Soil temperatures at our research center in North Brunswick have been well below this threshold as of this writing. At this time we are holding off on making pre-emergent applications to our research trials. However, in southern New Jersey soil temperatures are warmer and crabgrass will germinate sooner. In these areas, making a pre-emergence herbicide application soon would be timely. If you are worried you may be too late, scout bare areas with crabgrass carcasses, especially those on south-facing slopes, as crabgrass will germinate earlier in these areas.

Making pre-emergent herbicides applications early is not thought to reduce efficacy. However, if you are using dithiopyr (i.e., Dimension) it’s a good idea to wait until shortly after emergence and take advantage of the early post-emergence efficacy this product provides against crabgrass.

Of course don’t forget to consider your potential renovation/seeding projects this spring. If you are planning on seeding, do not apply any pre-emergence herbicide.

Literature Cited

Fidanza MA, Dernoeden PH, Zhang M (1996) Degree-days for predicting smooth crabgrass emergence in cool-season turfgrass. Crop Sci. 36:990-996.

Killing Freezes… Finally

Many people are pleased that typical winter temperatures have taken so long to show up. Below are some interesting observations from early- to mid-winter in New Brunswick.

Relatively warm soil temperatures (as high as mid-60s °F) stimulated growth late into December.

Dandelion bloom on 15 December 2015 in New Brunswick.

Dandelion bloom on 15 December 2015 in New Brunswick.

Had to remove cover (folded up in behind Kyle Genova) from our K-Microdochium Patch trial so that it could be mowed on 16 December 2016!

Removed the permeable growth cover (folded up behind Kyle Genova) from our K-Microdochium Patch trial to mow it on 16 December 2016!

 

 

 

 

 

 

 

Winter flush of seedheads on annual bluegrass

Annual bluegrass can go to seed about anytime of the year but this is a first for me — lots of annual bluegrass seedheads on 28 December 2015 in New Brunswick.

 

 

 

 

 

Kyle Genova pulled back permeable turf cover to inspect annual bluegrass growth and progress of the Microdochium Patch inoculation on 28 December 2015. Turf is still growing and disease is expanding.

Kyle Genova pulled back the permeable turf cover from the K-Microdochium Patch trial on 28 December 2015. The annual bluegrass was still growing enough to schedule another mowing. And the progress of the Microdochium Patch inoculation was expanding (good for the research but ugly!). No disease response to potassium at this point.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Odd to find weed species that are normally gone by this time of the year. Killing frosts/freezes are finally here and frost sensitive plants should be damaged and won’t persist much longer. Cool-season turfgrasses will transition into dormancy if freezing temperatures linger for a while. But it won’t be too long (66 days until spring, 20 March) before annuals like prostrate knotweed will germinate and start to emerge from bare soil areas.

Freeze Injury on Weeds

Don’t recall prostrate knotweed (annual) persisting into January. But freezing temperatures have finally killed the knotweed. Also note that the leaves of broadleaf plantain (perennial) have just now been frost damaged.

 

Winterkill on Annual Bluegrass: Don’t Skip the K

We lost the ice cover on our Poa annua trials two weekends ago (March 7-8th) and initially the turf looked okay. But now… it doesn’t. And it will probably get worse, if we are reading the symptoms correctly.

Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Photo taken 15 March 2015. Healthier looking turf has received K fertilization; dying turf has not.

Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Green, healthier looking turf received K fertilization; dying turf did not. (15 March 2015)

Last Friday (March 13), my graduate student, Chas Schmid, informed me that I needed to look at his potassium trial on our Poa annua turf. There was a huge difference between no-K and K fertilized plots. The no-K plots have steadily lost green color and become very blotchy. Plants taken from those plots are water-soaked and feel mushy when squeezed (How is that for a scientific description?). Dr. Lindsey Hoffman has a lot of experience with winterkill on Poa annua in Massachusetts and she is convinced that many of the plants are dead. And it smells like it – silage on a dairy farm!

Take home for me – don’t let your Poa annua turf become potassium deficient! Chas’ data for suppressing anthracnose severity indicates that a soil test (Mehlich 3) ≥50 ppm K and a tissue level of ≥2% K in the clippings are indicators that the K level is good. And winterkill in March 2015 hasn’t changed my mind about that data!

Looks like this might be the end of this Poa annua field. Dr. William Meyer said, “Good riddance.”

Brown Ring Patch Spotted in New Jersey

Brown Ring Patch (aka Waitea patch) is starting to show up on golf course putting greens at this time.  This disease is caused by the fungus Rhizoctonia circinata var circinata and typically develops during warm weather from April through June.  Symptoms start as small yellow rings (0.25-2 inches wide) with green grass in the center and can ultimately reach a foot or more in diameter. The yellow rings can turn an orange or brown color as the disease progresses.  Although the disease rarely kills turf, affected areas are extremely slow to heal.  For best results, apply Medallion, polyoxin-D (e.g., Affirm or Endorse), ProStar, one of the QoI fungicides (e.g., Heritage or Insignia), Trinity, Triton Flo, or Torque now and repeat in two to three weeks to limit disease development later this spring.   Unlike yellow patch, the brown ring patch fungus can degrade the thatch in infected areas so several fungicide applications are typically required to prevent significant damage.  Seedhead suppressants (e.g., Proxy + Primo) may enhance disease severity.  Therefore, be sure to initiate a preventive brown ring spot fungicide program in areas where this disease has been troublesome and seedhead suppressants have been applied.  For more information on brown ring patch, click here.

Brown ring patch on a golf green (Photo courtesy of S. McDonald)

Brown ring patch on a golf green (Photo courtesy of S. McDonald)

 

Annual Bluegrass Control in Kentucky Bluegrass

Unfortunately, we had annual bluegrass invasion into the 2011 Kentucky Bluegrass Trial, sponsored by the National Turfgrass Evaluation Program (NTEP). As a result, we are trying a relatively new herbicide, [Read more…]