Managing Thatch

Recently received a couple of questions about managing thatch.

One question was concerning the recent trend in the industry to not core putting greens and only use solid tines. 

Non-coring programs rely on topdressing to dilute the organic matter (thatch) that accumulates, thus forming a mat layer as opposed to a thatch layer. Turgeon defines mat as a tightly intermingled layer composed of [Read more…]

Cadmium and Phosphate Fertilizer Debated in EU

Fertilizer derived from phosphate rock, which naturally contains cadmium, is being debated in the European Union. More than half the cadmium, a toxic heavy metal, in some agricultural soils originated from phosphate rock derived fertilizer. Sedimentary phosphate rock mined in northern Africa contains naturally high cadmium levels. Phosphate from mines of igneous rock in Russia has much lower levels.  Read more…

Spring Weed Control Update

Weed Control Update

It feels like winter is hanging on and it looks a bit more Siberia-like than it did at this time in 2017. I’m writing this while watching the telecast of the Arnold Palmer Invitational in sunny Florida (where the greens are rolling PURE) and another snowstorm is taking aim at the Northeast. Interestingly, when comparing the 2018 GDD accumulation to 2017, things aren’t too different. We have accumulated about 300 GDD (using a base of 32 F) to date compared to 340 GDD at this time in 2017 in central New Jersey. However, things do look different when using a GDD model with a base of 50 F. We have accumulated 26 GDD50 to date in 2018 compared to 58 GDD50 at this time in 2017. Soil temperatures (3 inch depth) hit 50 F for a couple days in February, but have been hovering between 35 and 40 F ever since. So what does that mean for weed control?

 

Annual Bluegrass Seedhead Suppression

Using the based 32F GDD model (which in my opinion is more appropriate for this region the the base 50F model) we are within the optimum application window for spring ethephon (Proxy) applications. If you haven’t already applied and are making spring-only applications, later this week or early next week would be a good time to apply if the snow melts. If you made an application in the December, January, or February, you have a lot more flexibility on the spring application timing and can probably wait until near the end of the optimum GDD window. For more information on GDDs and annual bluegrass seedhead suppression see this previous blog post

 

Annual Bluegrass Seedhead Suppression

 

Our 2016-2017 seedhead suppression research (in collaboration with Dr. Zane Raudenbush at OSU-ATI) demonstrated that Proxy applied in December and twice in the spring provided better annual bluegrass seedhead suppression than two spring applications. Interestingly, a single Proxy application in December with no spring applications was very effective in both New Jersey and Ohio. We are currently repeating this research. I’ve been asked if Proxy applications in January or February instead of December would be effective. Dr. Shawn Askew’s research in the Mid-Atlantic region demonstrates that January or February applications are extremely effective, but this application timing has not been evaluated in the Northeast or Midwest where annual bluegrass tends to be more dormant in January and February than in the Mid-Atlantic. This concept is something we plan to explore in more detail next winter.

 

Crabgrass Control

The forsythia bush is an effective phenological indicator of crabgrass germination. When forsythia reaches full bloom, it is an indicator that the opportunity to apply crabgrass pre-emergent materials is about to pass. If you are using dithiopyr (Dimension) you can wait until shortly after crabgrass emergence to apply.

You may remember last year that in Central and Southern New Jersey, forsythia bloom began in early March and these early blooms were killed by a snowstorm. Forsythia full bloom occurred in early April 2017 (and crabgrass germinated in mid April), which was a bit earlier than normal. This year with more seasonal temperatures, buds are visible but we are still several warm days away from forsythia full bloom. We are also well below the 3-day 55 F soil temperature threshold that is another good indicator of crabgrass germination. The 5-day rolling soil temperature average has been below 38 F for the last week.

Forsythia buds in Central NJ on March 18.

 

The Bottom Line 

With this seemingly long winter you may be stir crazy or trying to find something to do besides clean up tree debris. In regards to weed management, be patient and make applications when the plants are ready. The soil is slowly warming and the sun intensity is increasing as we trudge towards spring. In the meantime, make sure your sprayer is calibrated and get the dust off your golf clubs. Spring is coming – allegedly.

Rectangles of Melting Snow

Made an interesting observation while inspecting this trial for geese damage last December; rectangular plots of snow melting faster than other plots. Not sure of ramifications, but snow cover on some treatments was melted or melting faster compared to other treatments. This trial has numerous combinations of topdressing sands and rates as well as hollow tine cultivation. The treatments with a drier surface were retaining snow cover longer than treatments that tend to retain more water in the surface 0- to 3-inches.

Rectangular areas of melted/melting snow on this research (putting green) trial are treatments that have greater water retention in the surface 0- to 3-inches.

Goosegrass

Goosegrass is a summer annual weed of cool-season turfgrass that has become more problematic in recent years. My conversations with turfgrass managers suggest that goosegrass is firmly entrenched as a top 5 turfgrass weed issue of highly managed systems in the Northeast region. Crabgrass is more prevalent than goosegrass, but is less problematic in highly managed systems because it is effectively controlled with pre-emergence herbicide programs.

Goosegrass is easily identified by its prostrate growth habit and white, compressed sheaths. Photo: E. Reasor

Goosegrass and crabgrass are both summer annual grassy weeds. So why do pre-emergence herbicides typically used in cool-season turfgrass (dithiopyr, prodiamine, and pendimethalin) often provide inconsistent goosegrass control? It should be noted that the pre-emergence herbicide oxadiazon often provides excellent goosegrass control but is not widely used in cool-season turfgrass.

One reason is that goosegrass seedlings are thought to emerge 2 to 3 weeks later than crabgrass and continue germinating later in the summer. Indeed, the research we conducted this summer to evaluate seasonal goosegrass germination patterns found that the first goosegrass seedlings emerged in mid May, about 3-4 weeks after the first crabgrass seedlings. Interestingly, when we calculated the time it took 90% of the plants to emerge, there was a big difference between our two locations. Ninety percent of the goosegrass seedlings had emerged by early July at the golf course location, but at the research farm location just a few miles away (soil temperatures were similar) 90% emergence occurred in mid to late August. But I digress…

If goosegrass germinates later than crabgrass, making split applications of pre-emergence herbicides should provide more consistent control than single applications. However, my conversations with many in the turfgrass industry suggest is that goosegrass has become more problematic only in the last 5 to 15 years regardless of application strategy and mitotic-inhibiting pre-emergence herbicides have been used widely for over 25 years. So this would suggest some other factors are in play.

On the same golf course where we found 90% of the total goosegrass seedlings had emerged by early July, we evaluated several pre-emergence herbicide programs for goosegrass control in 2017. Treatments were applied in early May. By mid June we noticed that plots treated mitotic-inhibiting herbicides had as much goosegrass as non-treated plots. Meanwhile, plots treated with oxadiazon (a different mode of action) had almost no goosegrass. For reasons mentioned earlier, I would not expect these mitotic-inhibiting herbicides to provide excellent goosegrass control, but they should be providing some control, especially in mid-June.

We collected seed from the site in December 2016 and we compared this seed to a population collected from our turfgrass research farm using a controlled experiment in the greenhouse. We found that the golf course population was not controlled by a mitotic-inhibiting herbicide, but the research farm population was 100% controlled (figure below). Both populations were 100% controlled by an herbicide with a different mode of action.

Pots treated with a mitotic-inhibiting pre-emergence herbicide on the day of seeding. The wild type population was collected from our turfgrass research farm. The golf course population was collected from a golf course with a history of mitotic-inhibiting herbicide use.

In the Southeast, herbicide resistance to mitotic-inhibiting pre-emergence herbicides (dithiopyr, prodiamine, and pendimethalin) and oxadiazon has been implicated as the cause of goosegrass issues on many golf courses and was first reported over 30 years ago in 1984 (by Mudge et al.). However, I’m not aware of resistance to mitotic-inhibiting herbicides in the Northeast despite heavy reliance on these herbicides for annual grassy weed control.

Goosegrass resistance to pre-emergence herbicides typically begins with one plant surviving the application due to a genetic mutation. The goosegrass plants with the mutation probably goes unnoticed and sets seed, which leads to a small patch of plants the next year when the same pre-emergence herbicide is used again and does not control plants with the mutation. The patch may become larger each year as that population is spread throughout the property via seed eventually becoming problematic.

At the recent NJ Green Expo in Atlantic City in December, I briefly discussed the topic of goosegrass resistance to pre-emergence herbicides during a panel discussion. Responses suggested this is an issue that deserves more investigation.

If you suspect that resistance to pre-emergence herbicides is an issue on your property, please contact me via email (matthew.elmore@rutgers.edu) or Twitter (@RUturfweeds). Your will be extremely helpful to help determine if this is a widespread issue and potentially collect plants/seed samples for further testing.. All correspondence will be kept confidential.

Winter Salt

At seminar lectures discussing the effects of turf fertilizer on water quality, I am often asked about the impact of de-icing salts on water quality. A recent article on winter road salt indicates that freshwater rivers are becoming saltier and more alkaline. Click here to read the article.

‘White soil’ along roadside indicates severe salt accumulation from winter de-icing.

Crabgrass and Goosegrass Control in Fine Turf

Over the past 7 to 10 days, warm-season weeds have really turned the corner and are growing rapidly. It’s probably no coincidence that 5-day average soil temperatures finally pushed past 70 degrees about 10 days ago in central NJ. Until last week, most of the crabgrass I observed was growing slowly with a chlorotic appearance. Now it has taken on the more characteristic lime green hue and is growing more rapidly than surrounding cool-season turf. Where previously it was mostly present in thin area of turf, it’s now beginning to make an appearance in dense stands of fine turf such as fairways and greens.

Smooth crabgrass with its characteristic hue in a poor stand of perennial ryegrass on June 23, 2017.

With this post, I’m going to focus mostly on control in in creeping bentgrass where herbicide options are limited. Now is a good time to scout historically problematic areas for small crabgrass and goosegrass plants. If left uncontrolled and allowed to tiller, crabgrass control in creeping bentgrass fairway turf is difficult and with risk of bentgrass injury.

Leaf stage smooth crabgrass in an annual bluegrass/creeping bentgrass fairway.

Fenoxaprop (Acclaim Extra) can be applied at 3.5 fl oz/A for control in bentgrass fairways. This rate is 8 to 10X lower than what can be applied to ryegrass, bluegrass and tall fescue to control larger crabgrass plants. At the 3.5 fl oz/A rate, multiple applications on 2 to 3 week intervals may be required to provide control of small leaf-stage crabgrass. If crabgrass is allowed to tiller, even multiple applications of fenoxaprop at rates labeled for use in bentgrass fairways may be a losing battle, so scouting is important. Quinclorac (Drive XLR8, Quinclorac 75DF) is an option to control tillered plants in bentgrass. At rates labeled for use in creeping bentgrass multiple applications may be required. Refer to the label for more information about rates, turfgrass tolerance and adjuvants.

Fenoxaprop will also provide suppression or control of small goosegrass plants. However, once goosegrass begins to tiller, fenoxaprop is less effective at low rates.

Topramezone (Pylex) is an effective herbicide for goosegrass control in cool-season turf. However, in creeping bentgrass fairways, Pylex is labeled for application at up to 0.25 fl oz/A. Tolerance may vary depending on bentgrass cultivar and other management practices. Topramezone causes bleaching of susceptible plant tissue and while limited bleaching is not detrimental to fairway turf from an agronomic perspective, it is very noticeable to even a casual observer. I hate to copy instructions from a bottle of carpet cleaner, but it’s a good idea to make an application to a small area of bentgrass and wait 10 to 14 days to make sure the bleaching you observe is acceptable. My experience with low rates of topramezone for goosegrass control is limited, but multiple applications may be required depending on plant size. Include methylated seed oil or crop oil with Pylex per the product label. Other cool-season grasses such as Kentucky bluegrass, ryegrass, tall fescue and fine fescue are more tolerant than creeping bentgrass and application at higher rates is permitted.

Crabgrass and goosegrass will continue to germinate throughout the summer. If you are observing significant breakthrough in areas already treated with a pre-emergence herbicide consider applying a pre-emergence herbicide with a different mode of action than previously applied. One example is Anderson’s Goosegrass/Crabgrass Control, which contains oxadiazon. Oxadiazon is a PPO inhibiting herbicide, not a mitotic inhibiting herbicide like most other pre-emergents (i.e., bensulide, dithiopyr, pendimethalin, prodiamine). Anderson’s Goosegrass/Crabgrass Control should be applied to dry turf and is labeled for use on bentgrass putting greens. Another example of an herbicide with a different mode of action is Tower (dimethenamid-P). Tower is labeled for use on bentgrass fairways and tees. Read the label for more information on turfgrass tolerance to both of these products.

For information on crabgrass and goosegrass ID and control other turfgrass areas, see this previous post.

The mention of trade names and rates is for educational purposes and does not imply endorsement by the author, Rutgers Center for Turfgrass Science, or the New Jersey Agricultural Experiment Station. Always defer to the product label for instructions on properly applying an herbicide.

Weeds off to a Slow Start

Despite a quick start to the spring, soil temperatures remain low across the much of the state. Average soil temperatures (3-inch depth) have been hanging around the mid 60s in central NJ and many warm-season weeds such as crabgrass have hardly developed despite germinating over 6 weeks ago. This crabgrass at our research facility has not advanced past the leaf stage and I have observed this across the region over the past few weeks.

Smooth crabgrass in the leaf stage

The peak of annual bluegrass seedhead production has passed. It was a very difficult spring to properly time ethephon applications for optimum seedhead suppression. If the results of our seedhead suppression research trial are indicative of the region, then I suspect those that made a fall (December at the snow mold fungicide timing) application of ethephon were happy with suppression. Spring-only applications did not perform very well in our research.

A very seedy annual bluegrass putting green at Hort. Farm No. 2

When warmer weather arrives, warm-season weeds will develop rapidly. If you are relying exclusively on post-emergence herbicides for crabgrass control, an application of a post-emergence herbicide in the next few weeks may be warranted. This will only control what has already germinated and not what will emerge as we continue into the summer, so additional applications will be necessary. Especially if using fenoxaprop (Acclaim Extra, Last Call), lower herbicide rates often can be used when treating smaller plants. Mesotrione (Tenacity) is another post-emergence crabgrass herbicide that is most effective on smaller plants. Quinclorac (Drive XLR8, Quinclorac 75DF) is another post-emergence option but is often more effective against larger (> 4 tiller) plants than the smaller plants present right now. Topramezone (Pylex) has efficacy some against crabgrass but is an extremely effective product for goosegrass control. See the herbicide labels for more information.

We observed goosegrass emergence two weeks ago at certain sites but not others. This event is not particularly relevant for those who applied a pre-emergent herbicide. However, you may want to scout areas with a history of goosegrass problems to make sure your pre-emergence herbicide is working. Goosegrass seedlings can be difficult to differentiate from crabgrass seedlings. Goosegrass seedlings have a ridged adaxial leaf surface (ridges look similar to perennial ryegrass) and a blunt leaf tip while crabgrass seedlings are relatively smooth with a sharper leaf tip. If you applied a pre-emergence herbicide and are already seeing goosegrass germination please contact me.

Goosegrass seedlings

If you plan to make an herbicide application to control broadleaf weeds, the weather continues to be ideal for control and growth of the cool-season grass into voids. This is especially true for the summer annual knotweed.

Prostrate knotweed observed mid-May in New Brunswick

 

Prostrate knotweed is more easily controlled now while it is still relatively immature. Standard three-way or other broadleaf herbicides that contain 2,4-D may not provide complete control. So in the case of severe infestation, products that contain triclopyr (e.g., T-Zone, Battleship III, 4-Speed XT, Cool Power, others) will provide more control. Cultural practices such as aerification to reduce compaction and improve conditions for turf growth are also essential. For more information on whether you will disrupt the pre-emergence herbicide barrier by aerifying, see this information from Dr. Aaron Patton.

To Aerify or Not to Aerify when Using a Preemergence Herbicide

 

Sedges and Kyllingas

This week I visited several golf courses and other sites along the Garden State Parkway from Exit 9 (Cape May) to Exit 171 (A few miles from the NY State line. In terms of plant development, northern NJ seems to be about a week behind central NJ and southern NJ seems to be a week or two ahead of central NJ. The most noticeable difference across locations is the difference in kyllinga emergence from dormancy. In southern NJ, kyllinga is close to full emergence while kyllinga northern NJ is at approximately 50% emergence. In all locations, but especially those in southern NJ, now would be a good time to begin making applications if you haven’t already.

False-green kyllinga dominating a stand of tall fescue

False green kyllinga (foreground) has a lime green color compared to the tall fescue (background).

 

Our research indicates that halosulfuron-methyl and imazosulfuron are effective options for control. Multiple applications will likely be necessary for effective control. Make follow-up applications after you observe re-growth from the previous application (usually 3 to 4 weeks later). For more information see this previous blog post by Dr. Murphy. https://turfblog.rutgers.edu/?p=934#more-934.

Soil Temperatures

Soil temperatures have been steadily warming since late March at Hort Farm No. 2 (North Brunswick). Temperatures consistently ran above 50 degree Fahrenheit in early April, and between 50 and 60 degrees from 10 to 27 April.

May 1st was the fifth consecutive day of the maximum soil temperature reaching at least 65 degrees. Thus, soil temperatures are essentially entering into an ‘ideal’ period for the growth of cool-season turfgrasses.

Those experienced with managing summer patch may recall that 5 consecutive days with a soil temperature maximum of 65 degrees is the threshold for initiating a preventive summer patch control program. Isn’t it ironic that ideal growth of the fungus that causes summer patch is synchronized with ideal growth temperatures for cool-season turfgrasses.

Damage from summer patch disease, however, typically is not seen until later in the summer when heat and drought stresses make it challenging for plants with a compromised root system to survive.

summer patch disease on hard fescue

Severe summer patch disease on hard fesuce at Hort Farm No. 2 in July 2013.

Some Early Disease Activity

Sorry no pictures for this post, but thought I would share some recent observations. The recent rains and warm night on Friday/Saturday brought out two diseases on annual bluegrass earlier than we typically experience at the research farm in North Brunswick NJ (Hort Farm No. 2).

Saturday morning, our graduate student found nickel- to quarter-sized spots of foliar Pythium on his annual bluegrass plots. Tended to be more spots on his plots with greater N fertility but the disease was also on low N plots. This is the earliest I have experienced foliar Pythium, but the Friday/Saturday nighttime temperature didn’t get much below 65 degrees F, ‘good’ for Pythium.

Also on annual bluegrass, was a slight outbreak of dollar spot on Saturday morning. Dollar spot in April is early but not unheard of in NJ.

You might notice that the pests mentioned have shown up first on annual bluegrass.