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.

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. http://turfblog.rutgers.edu/?p=934#more-934.

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.

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…]

Crabgrass Emerging

Crabgrass has been emerging for several weeks now, depending on the exposure. Warmer and more open turfs will likely have more advanced (larger) plants while cooler and denser turfs will have smaller plants.

Relatively small crabgrass plants  (most pre-tillering stage) emerging from a footpath on June 11th.

Relatively small crabgrass plants (most pre-tillering stage) emerging from a footpath on June 11th.

 

Management options for this weed at this point in the season range from doing nothing to [Read more…]

Green Kyllinga Found in North Brunswick

Uh-oh! We now have green kyllinga at Hort Farm No. 2 in North Brunswick. Joe Clark found it in a field that was sprayed with glyphosate. Most everything died but the kyllinga! Carrie Mansue has made some collections of kyllinga and will be doing some herbicide tests in the greenhouse this winter to determine which materials have the best activity on the this very difficult to control weed.

Keep a lookout for this weed, if left alone it will spread by rhizomes. Carrie has visited lawns that were essentially overrun by kyllinga. Once kyllinga achieves that level of dominance, control is nearly impossible without complete renovation. See previous post on the topic.

Live patch in foreground is kyllinga that survived a spray with glyphosate. Yellowed plants to left are yellow nutsedge.

Battling Green and False Kyllinga in New Jersey Turfs

We are seeing and hearing about increasing problems with green and false kyllinga; both are very troublesome invasive weed species that have moved northward into New Jersey. Green kyllinga and false green kyllinga are very similar in appearance, and both are referred to as green kyllinga. Green kyllinga is very difficult to control once large mats form.

These weeds thrive under mowing and are prolific in areas that are poorly drained or frequently wet. If you do not have [Read more…]

Are there Organic Alternatives to Glyphosate?

We receive requests for information on “organic” alternatives to glyphosate (e.g., Roundup), especially for “trim” sprays on paved areas, sidewalks, skin surfaces on ball fields, etc.

The research on organic non-selective herbicides that are being marketed as replacements to glyphosate (for example, Roundup) is growing but it is much more limited that what you can find on more conventional herbicides; however, we have been evaluating some products. Our results indicate that [Read more…]