Summer Aeration/Cultivation/Venting

Aeration during the summer can be a helpful practice but does need some caution. Many turf managers performing mid-season aeration on putting greens will be using needle tines, which are less disruptive. But the key words are [Read more…]

Glyphosate Alternatives

Recent news about glyphosate has many thinking about alternatives.

Joe Neal (Professor of Weed Science, Extension Specialist & Department Extension Leader Horticultural Science) and Andrew Senesac (Extension Weed Scientist Cornell Cooperative Extension, Suffolk Co., NY) have published a thorough summary of alternatives and the associated pros and cons through NC State Extension at https://content.ces.ncsu.edu/are-there-alternatives-to-glyphosate-for-weed-control-in-landscapes

Roughstalk bluegrass

Roughstalk bluegrass (Poa trivialis) is a cool-season perennial grass often considered a weed. Light green in color it is most obvious in the early spring when it grows more rapidly than other turfgrasses. As temperatures rise in the summer its growth will slow and it often goes semi-dormant until cooler temperatures and rainfall return in the autumn.

A roughstalk bluegrass plant in a lawn in spring.

A small roughstalk bluegrass plant with purple stems.

Infestations usually begin as small plants, but over time these plants spread via stolons and form patches that don’t tend to mix well with other cool-season grasses. These patches form as small plants expand from stoloniferous growth. These stolons (in addition to the lighter green color) can be used to differentiate roughstalk bluegrass from other bluegrasses such as annual bluegrass (no stolons or rhizomes) and Kentucky bluegrass (rhizomes only). Unlike Kentucky bluegrass, roughstalk bluegrass also has a long membranous ligule with a pointed tip.

Patch of roughstalk bluegrass in a lawn.

Patches of lighter green roughstalk bluegrass amongst Kentucky bluegrass

Currently there are no selective herbicides you can use in a home lawn to control roughstalk bluegrass. For many years Velocity herbicide was an option for professional turf managers, but it is no longer being manufactured and is not registered for use in home lawns (golf courses and sod farms only). Xonerate herbicide can provide some suppression, but should be used carefully to prevent injury to desirable turfgrass.

To control roughstalk bluegrass in cool-season lawns and athletic fields, nonselective control with glyphosate (Roundup and others) followed by reseeding is the best option. Apply glyphosate at this time in early spring, before summer stress, for best control. Glyphosate will kill any plant the spray contacts so apply carefully. If the areas are small, consider removing them with a shovel or a sod cutter. Be sure to remove the patch and at least 12 inches of turf surrounding the patch. Removing soil to a 0.5-inch depth should be sufficient to remove the stolons and all growing points. Reseed or sod the area with a desirable turfgrass species after removal.

These recommendations are based off of the 2019 Turfgrass Weed Control for Professionals guide. I highly recommend this guide for professionals managing cool-season turfgrass.

Insane Rain

The summer of 2018 isn’t going away quietly for many in New Jersey. August 2018 will be remembered for a steady dose of torrential rain that has made turfgrass management extremely difficult, especially in the northern half of the state. In the last 30 days, over 12 inches of rain have fallen across several counties in Northern NJ. This is almost triple the 30-year average of approximately 4 inches of rain for this period in a normal year.

These rains have produced saturated soils during an already difficult time of year for cool-season turfgrass (examined by Dr. Murphy in a previous post). High humidity and extended periods of leaf wetness have provided ideal conditions for diseases as well. Desirable turfgrass is thinning out and giving the competitive advantage to certain weeds. If you have weed problems right now you are not alone!

Nutsedge, false-green kyllinga, and creeping bentgrass (where it is a weed in poorly drained areas) are very competitive perennial weeds in wet soils and I’ve noticed they have become more prevalent in recent weeks. Even roughstalk bluegrass has awoken from summer dormancy in some spots.

Amongst annual weeds, crabgrass and goosegrass seem to be especially prevalent this year. Plants that escaped pre-emergence applications matured very rapidly through warm and wet conditions in late July through mid August and made post-emergence control difficult. Crabgrass and goosegrass are much more difficult to control as they mature beyond the 5-7 tiller stage of growth. With heavy rainfall and warm temperatures in late July it was difficult if not impossible to make post-emergence applications in time for optimal weed control.

Goosegrass plant with 4 tillers. Difficult, but not impossible to control.

Goosegrass plant with too many tillers to count. Extremely difficult to selectively control.

In a perfect world, post-emergence herbicide applications are not necessary due to an effective pre-emergence herbicide program. But grass, soils, and weather are not perfect and pre-emergence breakthrough in problem areas is expected. Pre-emergence herbicide programs were pushed to, or past the limit after heavy rainfall this spring. Late May was especially wet in the Central NJ where some areas received almost 10 inches of rain which fell during 11 days of a 17-day period (see CoCoRaHS for statewide maps). These conditions may have increased dissipation of pre-emergence herbicides, especially in sandy soils. Crabgrass breakthrough may be especially evident on slopes, high traffic areas, compacted soils, or where only a single pre-emergence application was made. Research consistently demonstrates that split application pre-emergence programs provide better crabgrass control than a single application and we are seeing history repeat itself in our 2018 crabgrass trials. Split application programs are providing excellent crabgrass control, and two most common pre-emergence herbicides (dithiopyr and prodiamine) are providing the same amount of crabgrass control at both locations. Keep in mind that in our research trials we subject herbicides to intense weed pressure, but the herbicides are applied uniformly under ideal conditions (immediate post-application irrigation, clipping return, non-compact soils) so we can make comparisons amongst treatments. Real world conditions may not be so ideal.

Excellent crabgrass control from a pre-emergence herbicide applied in early April and re-applied mid-June. Notice crabgrass pressure in the non-treated areas around the plot.

Less crabgrass control from a single application of a pre-emergence herbicide in April. In total for the season, the same amount of product was applied to both plots pictured.

 

Moving forward

Apply post-emergence herbicides if possible. Weed suppression that limits seed production is especially worthwhile on and around high-value sites (e.g., putting greens, athletic fields). Pylex (topramezone) is an excellent option for goosegrass control and crabgrass suppression in cool-season turfgrass. In my experience, applications at 1.0 to 1.5 fl oz/A will control multi-tiller plants (only 0.25 oz/A is permitted in creeping bentgrass). Tank-mixtures of Pylex and SpeedZone also provided excellent goosegrass control in our 2018 research. This tank-mixture will be evaluated more in 2019 as an option in Kentucky bluegrass, perennial ryegrass, and tall fescue. Quinclorac products (Drive XLR8, Solitare, generics) that can be applied at up to 0.75 lbs quinclorac/A are more effective than Pylex on crabgrass in cool-season turfgrass (lower rates can be used in creeping bentgrass) but will not control goosegrass. Tank-mixtures of Drive XLR8 and Pylex are safe to Kentucky bluegrass, tall fescue, and perennial ryegrass in my experience. Acclaim Extra (fenoxaprop) is another good option that will provide multi-tiller crabgrass and goosegrass control at higher rates. See product labels for more information on turfgrass tolerance, tank-mixtures, and weed control efficacy. Be sure to read the label carefully for information on adjuvants. Not including an adjuvant, or using the wrong one will severely reduce the efficacy of many post-emergence herbicides. For even more information, an excellent guide for weed ID and herbicide selection can be found here at the Purdue University Bookstore. I highly recommend this comprehensive guide.

More importantly, use fertilization and cultural practices to encourage recovery of the cool-season turfgrass once temperatures are more favorable and cool-season grasses regain the competitive advantage (hopefully around labor day). A strong stand of turfgrass will be more competitive against winter annual weeds and crabgrass in 2019. Even in cases of severe crabgrass or goosegrass infestation, a total kill of the existing turfgrass stand is usually not necessary if there is a good base of desirable turfgrass lurking beneath the crabgrass. Use selective herbicides, seed, cultural practices, fertilizer, and September weather to your advantage.

Summer Patch on Hard Fescue

Hot weather in early July brought on some severe summer patch (root disease) symptoms in hard fescue. This disease on fine fescues hasn’t been as thoroughly studied as it has been on other grasses.  So recommendations are based on knowledge learned in Kentucky bluegrass (Poa pratensis) and annual bluegrass (Poa annua) turfs. We are establishing plots this summer and fall to learn more about this disease on hard fescue.

Symptoms of summer patch disease on a 4-year-old hard fescue turf in New Brunswick NJ.

Fine fescues are better adapted to dry and infertile soils. Summer performance of fine fescue will generally be better in moderate to light shade than full sun.

To limit damage from summer patch on fine fescues, do not apply more than 2 lbs. of N per 1,000 sq. ft. per year. An acidifying form of N such as ammonium sulfate is thought to be the best choice when fertilizing fine fescues affected by summer patch. Caution is needed when irrigation fine fescue turf, especially on heavy (loamy) soils. Summer patch disease tends to be more severe on soil that retains water. Irrigation should be applied in a manner that moistens the soil after some time of drying but does not keep the soil excessively wet for many days. Mow fine fescue turf no lower than 2.5 to 3 inches and stop mowing when the turf shows symptoms of heat and drought stress in the summer. Fine fescue turf grows more slowly than other cool-season turfgrasses especially when air temperatures approach and exceed 90 °F.

See Dr. Bruce Clarke’s PowerPoint slides for more details on summer patch disease.

 

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.

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!