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.

Warm Air, Cool Soil

Warm air temperatures build anticipation of plant growth but keep in mind that cool soil temperatures will strongly moderate growth during the spring. Turf growth typically will be very slow until [Read more…]

Winter Damage

 

snow plow damage

Sod pieces removed by snow plowing.

While the warm weather has allowed many of us to get out and enjoy the outdoors, you may have noticed [Read more…]

Annual Bluegrass Seedhead Suppression

In weed management on golf courses, annual bluegrass (Poa annua) seedhead (inflorescence) suppression often kicks off the growing season. Plant growth regulators can be used to suppress seedhead production if applications are properly timed. Much like pre-emergence herbicides that are not effective if applied after weed emergence, PGRs are less effective if applied too late.

It is common to make two or three sequential applications of trinexapac-ethyl (i.e., Primo Maxx, T-Nex) + ethephon (i.e., Proxy, Ethephon 2 SL) or ethephon alone in the spring. Timing the first application can be difficult. One method is to make the first application at the first sign of the “boot” stage. Annual bluegrass is considered in boot stage when the stem is swollen, indicating that it contains a seedhead (pictured below).

A swollen annual bluegrass stem indicating this plant is in the “boot” stage.

If the leaf tissue is carefully removed from the stem layer by layer, it will reveal the inflorescense (pictured below), which you can usually see with your naked eye or the aid of a hand lens.

A relatively immature inflorescence of annual bluegrass visible after plant dissection and the aid of a dissecting microscope.

A more mature seedhead visible to the naked eye after stem dissection.

This seedhead will continue to move up the stem, eventually emerging. Once the seedhead emerges from the stem the plant is considered post boot stage. Using the boot stage method to time applications requires careful inspection of several plants at various times during the spring. To predict booth stage on a putting green, it is best to check south facing slopes and higher cut turf, as seedhead emergence in these areas will be ahead of putting greens.

Growing degree-day models have been developed as alternatives to boot stage-based PGR application timings. One model developed by Dr. Ron Calhoun at Michigan State University (gddtracker.net) uses a base temperature of 32 degrees F and a target of 200 to 500 GDD with accumulation beginning February 15th. However, to my knowledge this model has not been validated in the Northeast region. The unusually warm winter may make this model less reliable. On the day this was written, our research farm in North Brunswick has accumulated 40 GDD32 since February 15th. If the weather occurs as predicted, we may reach 200 GDD32 by Sunday February 26th when more seasonal weather returns.

Another GDD model common to the Northeast region uses a base temperature of 50 degrees F and a target accumulation of 50 GDDs beginning February 1st. However, I am not aware of any published literature validating this model in this region. On the day this was written, our research farm in North Brunswick has accumulated 8 GDD50 since February 15th. If the weather occurs as predicted, we may reach 30 GDD50 by Sunday when more seasonal weather returns.

A combination of GDD tracking and scouting for boot stage may be useful to time PGR applications. Scout roughs and bare areas with annual bluegrass for boot stage and seedhead emergence. As we approach the GDD threshold, scout roughs, fairways, and greens more intensely for boot stage and seedhead emergence. Boot stage is typically observed in late March or early April in New Jersey so we are still likely several weeks away. However, if temperatures remain warm it may arrive earlier this year.

Recent research from Dr. Shawn Askew at Virginia Tech has demonstrated efficacy of ethephon applications made just before winter dormancy followed by spring applications of trinexapac-ethyl + ethephon. We have a trial underway at Rutgers to evaluate the efficacy of fall applications in this region in collaboration with Dr. Zane Raudenbush at Ohio State. In addition to validation of this fall application strategy in multiple regions, research to ensure fall or winter applications of ethephon do not increase the potential for annual bluegrass winterkill may be necessary. For more information on Dr. Askew’s research visit http://www.golfdom.com/a-new-key-to-poa-annua-seedhead-suppression/

Fun Fact: Annual bluegrass seed can become viable even if the seedhead is removed from the plant on the same day it is pollinated. Just another reason this weed is so competitive in turfgrass!

Note: Embark (mefluidide) also provides excellent annual bluegrass seedhead suppression when used properly, but it is no longer being manufactured.

We will continue to scout for annual bluegrass seedhead emergence. To share your own observations and for updates from Rutgers, follow @RUturfweeds on Twitter!

Weather Ideal for Pythium and Brown Patch

The weather this summer has been very conducive for brown patch and Pythium blight diseases. I have received number requests this summer to address turf problems related to one or both of these diseases in lawns, sports fields, sod and now my own plots.

Suspected initial outbreak of Pythium on velvet bentgrass maintained at a 0.110-inch height that occurred over the weekend (August 7) in a cultivation trial at Hort Farm No. 2 in North Brunswick NJ.

Suspected initial outbreak of Pythium on velvet bentgrass maintained at a 0.110-inch height that occurred over the weekend (August 7) in a cultivation trial at Hort Farm No. 2 in North Brunswick NJ.

The weather forecast for the rest of this week indicates [Read more…]

Licensing for Mosquito Control – Category 8B

I have been getting questions from landscape/turf professionals about licensing for mosquito control. I asked Dr. George Hamilton about where to direct professionals with these questions.

Information on licensing of professionals for mosquito control can be found on the Rutgers Cooperative Extension Pest Management website: http://pestmanagement.rutgers.edu/PAT/

You can get a core manual and category 8B manual at your county extension office.

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.

 

Kyllinga Awakens as Soil Temps Increase

Daily high soil temperatures at the 2-inch depth are consistently getting into the 60s °F. Yesterday, temperatures in sunny locations reached into the upper 60s. This means that the warm-season species are, or will be soon waking from winter slumber.

Leaf tips emerging from rhizomes of kyllinga on 15 April 2015 in central New Jersey.

Leaf tips emerging from rhizomes of kyllinga on 15 April 2015 in central New Jersey.

For the last three weeks, I have been watching the emergence of false green kyllinga (Kyllinga gracillima). Most sites infested with kyllinga are probably showing active shoot growth. So it appears that kyllinga needs soil temperatures that reach consistently into the 60s to emerge from winter dormancy. As temperatures continue to warm, re-growth of kyllinga should accelerate.

False green kyllinga is a perennial sedge species with well-developed rhizomes (underground lateral spreading stems). Kyllinga is relatively low growing so it [Read more…]

Looks Like Grass… But It Isn’t

Other than today and yesterday, soil temperatures in New Brunswick have been reaching into the lower 50s °F during the last week or so. And you see the effects, some plants are finally awakening from winter slumber. Cool-season turfgrasses are slowly greening up. Tree buds are swelling, some are flowering. Forsythia is just starting to bloom. And prostrate knotweed, one of the earliest germinating summer annual weeds, is emerging.

Prostrate knotweed is frequently found invading [Read more…]

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.”