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.

Dog Days and Cool-Season Grass

 

Cool-season lawn struggling to grow in shallow soil on a south-facing slope during dog days.

According to Merriam-Webster, dog days is the period between early July and early September when the hot sultry weather of summer usually occurs in the northern hemisphere; a period of stagnation or inactivity.

The dog is actually the Dog Star – also called Sirius – which rises simultaneously with the sun during the hottest days of summer in the northern hemisphere. Plutarch (Greek writer, 46-120 AD) referred to the hot days of summer as hēmerai kynades (literally, “dog days”); the Latin translation dies caniculares is the source of our English phrase. But I digress…

You most likely have noticed that cool-season grasses have recently entered a period of stagnation or inactivity (dog days) and, in some cases, are spent. The hot summer days have steadily increased soil temperatures to the point that the soil is now warmer than air temperature for much of the daylight hours and all of the night. During the last 10 days at Hort Farm No. 2, soil temperature at 3-inches has oscillated between 76 and 90 °F and at 2-inches 78 and 92 °F. These soil temperatures are well above the optimum temperatures for root growth and clearly explain why cool-season grasses are lethargic at this time.

What to do? Be patient and do not “push” the grass. This is not the time of year to stress out turf – the grass has very little resiliency and will not tolerate much abuse or recovery quickly. I recently witnessed utility vehicle traffic on subtly drought stressed turf during the hottest part of the day result in classic tire-track damage. Root systems of cool-season grasses are weakest and shallowest at this time of year. Thus, localized drought stress can develop rapidly – within a couple hot, sunny days – during the dog days.

These cultural practices can be helpful in getting high value turf to survive dog days. Once the turf has drained after drenching thunderstorms (2-3 days), program daily, very-light (50-65% of reference ET), deficit irrigation using a rainhold setting (such as 0.2-inch rain) to stop irrigation from adding to over-wetting from storms. Deficit irrigation assures that thunderstorms will be the reason for excess wetness, not the irrigation schedule. This irrigation plan should encourage the turf the dry without over-drying between irrigations (or thunderstorms). If excess drying does occur with this irrigation plan, it probably will start in highly localized (small) areas, which can be effectively managed with well-timed syringing to re-hydrate dry leaves and prevent crispy thatch during the heat of the day. Crispy thatch means that surface adventitious roots either are or will soon be crispy as well. Moist to dry thatch is good, whereas crispy and crunchy thatch in the heat is bad. Weekly, low-rate fertilization (N and possibly P, K and micronutrients) is crucial on sand-topdressed and sand-based rootzones commonly found on golf course putting greens and some sports turfs. These rootzones have very little mineralization capacity to supply essential nutrients during dog days. Weekly low-rate fertilization provides a steady, consistent slow-growth and avoids the “surge-crash” cycle of growth that results from less-frequent and higher application rates. Typically, low-rate N is no more than a 0.1-lbs. per 1,000-sq. ft.

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.

 

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.