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Jim Murphy

Tis the Season for Summer Stress

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Optimum growth of cool season grasses occurs within the temperature range of 60 to 75 °F. Yesterday, the New Brunswick weather station indicated that soil temperature at 2 inches exceeded 75 °F for more than 12 hours and peaked at 82 °F.

This doesn’t mean that grasses will soon be dead. But it is a signal to be watchful for summer stress problems.

Summer stress is often a combination of multiple stresses. Localized drought, ponding of water, diseases, insect pests, poor culture (mowing, fertilization, and irrigation) and other stresses combined with high temperature stress can challenge the health and persistence of cool season turfs from now through the end of summer. It is important to avoid situations that compound too many stress at the same time.

For example, now is the time [Read more…] about Tis the Season for Summer Stress

Right On Cue: Dollar Spot Disease

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Exactly like Dr. Bruce Clarke teaches, Memorial Day arrives and so does dollar spot disease.

Symptoms appear as round, brown to straw-colored spots approximately the size of a silver dollar. On short cut turf, the spots with advanced damage can become somewhat sunken. At taller cutting heights (greater than 1 inch), the damaged spots are larger and more diffuse.

Highly susceptible grasses will be the first to exhibit symptoms including annual bluegrass, creeping bentgrass (depending on cultivar), and perennial ryegrass. Tall fescue and most Kentucky bluegrasses will be more tolerant of this disease.

Cultural techniques that can suppress dollar spot disease include disruption of dew and guttation water in the morning and increasing N fertility (if it is low). Mowing early in the morning (disruption of dew) should also be helpful.

Creeping bentgrass.
Creeping bentgrass entries in Dr. Stacy Bonos’ evaluation trials that are highly susceptible to dollar spot disease appear in the image foreground.

Update: Green-up of Turf

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Most landscape lawns, sports turfs, and golf course surfaces should have reached full green-up but there will be some exceptions. The major exception to this is zoysiagrass turf. Zoysiagrass will not begin green-up until mid- to late-May. Although not as slow to green-up as zoysiagrass, fine fescue will be slower than perennial ryegrass and tall fescue. Many of the Kentucky bluegrass varieties that are commonly used for sod production will be slow to green-up in the spring.

Dormant zoysiagrass with patches of perennial ryegrass in a home lawn.
Dormant zoysiagrass with patches of perennial ryegrass in a home lawn.

Lawns that are predominately fine fescue lawn should not be aggressively fertilized with nitrogen; do not apply more than 0.5 lb. of N per 1,000 sq. ft. unless the fertilizer contains 30% or more slow release nitrogen. Even with slow release N, applications to fine fescue should not exceed the 0.75 to 0.9 lb per 1000 square feet range during the spring. Over-fertilizing fine fescues could lead to serious summer stress problems including poor heat and drought tolerance.

A predominately hard fescue lawn.
A predominately hard fescue lawn that has not reached full green-up in late April. Avoid overfertilizing fine fescues to force green-up. Serious summer stress problems could develop.

Slow green-up of Kentucky bluegrass can be overcome to some extent with N fertilization. Fertilization in the spring will not cause the same summer stress problems with Kentucky bluegrass compared to fine fescues. But care should be taken to avoid over-fertilization. Over-fertilization problems on Kentucky bluegrass are more likely to be evident over multiple growing seasons rather than a single season. Excessive thatch build-up is the major problem of over-fertilizing Kentucky bluegrass, which typically expresses as a severely drought-sensitive turf (roots are growing in thatch, not soil). The total amount of N applied to Kentucky bluegrass during the spring should be within the range of 0.5 to 1.9 lbs. per 1000 square feet. Application rates above 0.7 lb. per 1000 square feet should include slow release nitrogen to limit surge growth and protect against N leaching.

Rectangular plots with a tinge of tan-color.
Rectangular plots with a tinge of tan-color are varieties of Kentucky bluegrass exhibiting slow spring green-up (photo taken 18 Apr. 2014).

Turf Green-up Underway

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It has been a long winter and delayed spring this year but yesterday’s rain and that of two weekends ago has “primed the pump” and initiated new growth of many turfgrasses and other plants. Thus, there is no more time to put off yard clean-up. Any leaves, branches and other debris dropped and blown around during the winter should be removed from turfs and other lowing growing landscape plantings. Otherwise early spring growth of plants will be impeded by any debris smothering those plants.

A lawn and a street.

There has been little to no leaf growth of turf to this point, so mowing isn’t needed other than for help in picking up or mulching tree leaves.

For turfs forming a complete and dense ground cover, there is no urgency to fertilize. Let the grass wake up in response to warmer weather and rain. If it is important to get the grass growing, apply low to moderate (0.25 to 0.5 lb. per 100o sq. ft.) rates of nitrogen fertilizer. Fast acting fertilizer will obviously encourage more rapid green-up. Some examples of fast acting N included ammonium sulfate, blood meal (natural organic), fish meal (natural organic), and urea. Do not apply more than 0.5 lb. per 100o sq. ft of a fast acting fertilizer at this time. Over-applying nitrogen in the spring could result in extremely fast growing grass once the weather warms into the 60 to 70 degree F range. It is also increases the risk for nitrogen leaching in locations where that is a concern.

A lawn and a pond.

For turfs that have poor ground cover, be aware that soil erosion will be a serious risk at this time of year. Soils are wet and easily eroded during intense spring rains. Remember that soil erosion and water runoff from bare ground can carry nitrogen and phosphate into our waterways, contributing to the eutrophication process. Take action to stabilize the soil in these areas. If turf is the intended vegetative cover, apply a seed blend or mixture containing perennial ryegrass to these areas to re-establish cover and stabilize the soil. Perennial ryegrass will germinate under cool soil temperature and is useful in re-establishing cover. If you want to delay seeding until the weather is warmer, cover these areas with a wood mulch to reduce the soil erosion and runoff that will occur during each rain.

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.

“Rain Shadows”

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Many people are aware that tree root competition is part of the challenge of maintaining turf within the drip line of trees. But the canopy of trees also contributes to the challenge by capturing and retaining much, and in some cases all, of a rain.

Rain shadows have been evident for some time now but the damage from the soil dryness has reached moderate to severe levels over the last couple weeks. Many of the lighter rainfalls over the last month haven’t wet the grass let alone the soil under large trees at Hort Farm No. 2 in North Brunswick.

The cumulative effects of a "rain shadow" and tree root competition lead to drought stress under trees.

Green Kyllinga Found in North Brunswick

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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.