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Drought and Heat

Time to Control Yellow Nutsedge

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Now is the ideal time to control yellow nutsedge (Cyperus esculentus). This plant is a perennial that grows best during the heat of summer and survives the winter through underground tubers. While the drought may have limited nutsedge emergence in unirrigated areas, it is visible and rapidly growing in irrigated beds and lawns.

Yellow nutsedge and other sedges look similar to grasses, but sedges have a unique triangular stem. This triangular stem results in a three-ranked leaf arrangement. While many sedge species can be found in the lawn and garden, yellow nutsedge is the only perennial sedge found in New Jersey and is far more difficult to control than annual sedges.

A cross section of a yellow nutsedge stem. This triangular shape is unique to sedges.
A yellow nutsedge plant from above. Notice the leaves at 120-degree angles from one another forming a three-ranked leaf arrangement.

Yellow nutsedge is a perennial through tubers. The aboveground plants and rhizomes are killed each winter and the tubers are the source of the infestation each spring. Initiating nutsedge control measures now will prevent the formation of new tubers and make this weed less problematic in the future.

Yellow nutsedge tubers.
Yellow nutsedge tubers. The brown tubers are mature while the white tuber is immature.

Lying dormant during winter up to several inches below the surface, nutsedge tubers sprout in spring, giving rise to new plants aboveground. These plants then produce rhizomes (underground stems) that form more plants and tubers for next year (and beyond). If left unchecked, a single tuber sprouting in spring can produce thousands of new tubers by the end of the summer.

A severe yellow nutsedge infestation.
A severe yellow nutsedge infestation in a recently mulched landscape bed. The open space between ornamental plants allows ample sunlight and nutsedge thrives.
Yellow nutsedge in a lawn in early June.
Yellow nutsedge in a lawn in early June is relatively inconspicuous. The thin and light green leaves are the nutsedge. The nutsedge will become more obvious as temperatures increase through the summer.

Implementing strategies to control nutsedge now before it forms tubers is critical to get rid of this weed. Right now in early June, yellow nutsedge shoots are producing rhizomes but have probably not yet begun producing tubers. Treating nutsedge with herbicide now and again in 6 to 8 weeks (if green shoots are visible) is an ideal strategy.

Yellow nutsedge rhizomes.
Yellow nutsedge rhizomes

The herbicide halosulfuron can be used for selective sedge control in both lawns and ornamental beds. It is safe to the turfgrass and can be applied around ornamental plants. Numerous formulations are available for professionals. A user-friendly product for non-professionals is Sedgehammer®+, which is widely available and sold in small pouches with the exact amount to mix into a gallon of water for a pump sprayer. This product also contains the surfactant halosulfuron needs for best nutsedge control. Halosulfuron is systemic (moves in the plant), but slow to work, so it will be 2 to 4 weeks before there are noticeable results.

Nutsedge tubers can persist for several years in the soil, so one year of herbicide treatment will not eliminate yellow nutsedge. But treating now and once more later in the season will reduce the severity of the problem in future years. This approach is better than waiting until mid or late summer for the first application.

Combine herbicide programs with non-chemical management to improve control. More than other weeds, nutsedge is poorly competitive in shade and in dry soils. You may notice nutsedge in thinner areas of the lawn. Focusing on turf management practices that increase lawn canopy density during the autumn (e.g. N fertilization and seeding) will result in fewer herbicide applications the future. Do not apply halosulfuron sooner than 4 weeks before seeding turfgrass. Modifying landscape beds to reduce large spaces between plants can be similarly combined with herbicide programs for better long-term control. Fixing poorly drained areas and being careful not to over irrigate may also help manage nutsedge.

It is possible to eliminate yellow nutsedge by hand weeding or by using OMRI-approved herbicides (which are non-systemic). But keep in mind, pulling shoots or killing with non-systemic herbicides usually signals the tubers to produce many new shoots. So, hand-weeding or spraying more frequently than with systemic herbicides like halosulfuron is necessary. Digging the tubers is not practical as they are several inches underground and many are too small to be easily seen.

Tropical Storm Brings Rain But What About Gray Leaf Spot?

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The passing of tropical storm, Fay brought some needed precipitation to the region, albeit too much at once in many places. Relatively dry soils (assumes not being over-irrigated) and the long, warm days of summer should allow turfs to dry out reasonably fast.

But what about gray leaf spot? Spores of the pathogen are thought to be blown up from southern regions to the north on the winds of tropical systems. With the recent passing of Fay, Dr. Bruce Clarke recommends being on the watch for early symptoms and signs of gray leaf spot outbreaks. Gray leaf spot can be severe on older, non-tolerant cultivars of perennial ryegrass while new, improved cultivars will be much less sensitive although not immune. Over the last couple years, we have also experienced some strong outbreaks of gray leaf spot on tall fescue across the region. So don’t ignore the tall fescue turfs if you have some.

For more information, see the fact sheet, Integrated Control of Gray Leaf Spot on Perennial Ryegrass.

Gray leaf spot control with fungicides on perennial ryegrass.
Fungicide plots on a perennial ryegrass cultivar that is highly susceptible to gray leaf spot.

Soil Health

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Soil that has been severely compacted often breaks into large massive plates.

For those interested in soil health – we all should be – the Soil Health Institute has release a 60-minute documentary featuring innovative farmers and soil health experts from throughout the U.S.

You can view the film at https://livingsoilfilm.com/

 

Dog Days and Cool-Season Grass

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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

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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.

 

Localized Drought Stress is Here

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As stated in an early post, summer stress is developing throughout the state. Summer stress isn’t widespread or severe but it is developing, particularly wilt stress, within very localized areas of many landscapes. Landscapes that receive little to no irrigation are especially prone to wilt and drought stress right now.

It is important to scout and assess the severity of any wilt stress in moderate-to-high value areas of the landscape. Hours are important, don’t put off the scouting of wilt stress. Assuming the grass or other plants will tolerate wilt stress without confirming the severity of the situation can lead to severe drought stress and stand loss at this time of year.

Symptoms of subtle wilt stress.
Symptoms of subtle wilt stress on June 22. Healthy turf will likely to tolerate this level of wilt stress.

Grasses such as the fine fescues and annual bluegrass will be

[Read more…] about Localized Drought Stress is Here

Drought Ends in New Jersey

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Last autumn I was blogging about the drought conditions that we were experiencing. Thankfully, this winter’s precipitation, albeit lots of snow, has changed our water status in the region. The U.S. Drought Monitor no longer lists New Jersey as having abnormally dry or moderate drought. You can view more details at http://www.nrcc.cornell.edu/page_drought.html

Expect I will have to post about snow mold disease and flooding, once we get a thaw.

A drought monitor map of the Northeast.
The current drought monitor map of the Northeast.

Abnormally Dry to Moderate Drought Condition in Much of NJ

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I mentioned in my previous post that dormancy has been apparent in many non-irrigated turfs. These conditions still persist throughout the central and northern NJ.

You can view the distribution and severity of the dry conditions throughout the northeastern U.S. at http://www.nrcc.cornell.edu/page_drought.htmlThis map shows that southern NJ is not experiencing drought conditions; whereas, central NJ is experiencing abnormally dry conditions, and northern NJ is experiencing moderate drought. This dryness typically doesn’t last through winter but it is something to watch. Moreover, you should assess your landscapes for any potential susceptibility to winter desiccation.

I want to share a some observations and ideas that have  come up while discussing this topic with turf managers.

  1. In those areas experiencing limited rain this fall, there has been very little recovery from summer stresses on non-irrigated turfs (and other plantings). These turfs may benefit from an application of a slow release N source to ensure recovery starts when water levels improve in late winter and early spring. Recall that NJ prohibits N applications to turf by professionals after December 1st (except on golf courses).
  2. While dry soil conditions this fall may have induced dormancy of the grass, the grass may be vulnerable to extended dryness through the winter especially in localized areas of turf that are sloped (water runs off) and exposed. These dry areas could experience desiccation damage if there are cold harsh winds combined with little to no snow or rain. If feasible, some irrigation of these areas before winter sets-in may be helpful in avoiding winter damage.
  3. Localized dry areas may have developed water repellency (become hydrophobic). These areas could benefit from an application of wetting agents to improve infiltration of rain and snow melt into the soil. Even if the soil is not hydrophobic, wetting agents will improve water infiltration of irrigation or winter precipitation.

Let’s hope that precipitation becomes more typical where it is currently dry.

Have a Happy Thanksgiving!

Dormancy in October? It is very dry and cool.

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I spent a couple days this past week teaching in a turf care training program at Central Park in NYC. Many lawn areas in Central Park that are not irrigated were entering dormancy because of the dry soil conditions. And as you look around there is an increasing acreage of turf as well as shrubs and trees in our area that are being challenged by drying soil conditions. Fortunately, it is cool and many plants are tolerating the drying by entering dormant.

Lawn area entering the onset of dormancy. Shoot growth is shutting down and leaves are wilting.

However, managers should think about their end of the season programs related to irrigation shut down [Read more…] about Dormancy in October? It is very dry and cool.