What Lies Beneath: Ice?

Dr. Kevin W. Frank

Associate Professor & Extension Turfgrass Specialist

Michigan State University

Some might remember 'What Lies Beneath' as the title of a horror movie but currently ice is a real life potential horror for golf course superintendents worried about winterkill. 

Weather Scenario

The winter of 2013-2014 will be remembered for many years to come. The first significant event was the ice storm of Dec. 21-22 that knocked out power for thousands and coated everything, included exposed turf, with a perfect coating of ice. 

Tall fescue encased in ice.

Most turf areas were covered with snow prior to the icing event and as the rain percolated through the snow it formed a very porous, crusty ice-snow layer.  This type of ice-snow layer is not a concern for turfgrass as it is porous and allows for gas exchange from the turf/soil interface to the atmosphere.

  

Two inch porous snow-ice layer + 1 in. snow on top.

Five days after the ice storm (Dec. 27) temperatures at the Hancock Turfgrass Research Center (HTRC) warmed to 38 °F and were accompanied by 0.15 in. of rain. On Dec. 28 and 29 temperatures were above 40 °F.  The warm temperatures resulted in melting and I believe this is when the first ice layer formed.  On Dec. 30 temperatures dropped and we all learned what a Polar Vortex meant as day time high temperatures were in the single digits and nighttime lows were well below 0 °F.  The Vortex combined with a foot or more of snow closed MSU for Jan. 6 and 7 but by Friday Jan. 10 the HTRC recorded a daytime high temperature of 38 °F and by Jan. 13 the high temperature was 44 °F.  This resulted in another melting event and another ice forming event as temperatures in the day melted snow and nighttime temperatures refroze any remaining water.   Some superintendents that were clearing snow from putting greens throughout the winter may have been successful at removing any ice that existed or formed during these melts.  However, depending on available labor and equipment many superintendents are not able to constantly remove snow during the winter so ice formation is inevitable. Since the melting ended on Jan. 13-14 the temperatures have been well below the point where any further melting would occur.  Not every green at the HTRC is covered in ice but at least one poorly draining Poa annua putting green is now covered in a 1-2 inch ice sheet.  I believe this ice sheet initially formed during the Dec. 28-29 melt so as of today (Jan. 29) the Poa has been under ice for 31 days.   

Two inch ice sheet on Poa annua green at HTRC.

Ice Sheets

In Michigan especially for Poa annua greens, crown hydration and subsequent refreezing are often the primary culprits of winterkill. However, this year ice sheets are a cause for concern.  In the 1960’s James B Beard conducted research at MSU on survival of creeping bentgrass and Poa annua under ice sheets.  Creeping bentgrass survived 120 days of ice cover without significant injury while annual bluegrass was killed somewhere between 75 and 90 days of ice cover. More recently Darrell Tompkins conducted research at the Prairie Turfgrass Research Center in Canada that suggested Poa annua greens could be damaged in as few as 45 days under ice.  The primary cause of death to turfgrass under ice sheets is most likely from toxic gas accumulation under the ice sheet from soil and turfgrass respiration.  The day estimates for turf survival are just that, estimates, use them as a guide but know that they are not absolutes.

Remove Ice?

Whether or not to attempt ice removal is a difficult decision for golf course superintendents.  The decision to remove ice can be based on several factors including: turf sampling, duration of ice cover, current and future temperatures, ability to remove water following melting from the green, and labor.

1. Sampling – Bob Vavrek from the USGA recently posted a great YouTube video http://tinyurl.com/k9mbfjc on how to sample greens under ice to assess survival.  An important point that Bob makes is that there is variability in sampling and just because your sample comes out alive doesn’t mean all areas on the green will survive – same can be said if your sample is dead.   

2. Duration of ice cover – as discussed in the previous section, estimates of days of ice cover causing death vary from 45-90 for Poa annua and 120 days for creeping bentgrass.  At this point I’m less concerned for creeping bentgrass surfaces as I’d expect significant melting before we reach a 120 day threshold as this would be well into April.  Poa annua is less certain as at the HTRC we will approach 45 days under ice cover by mid-February.  Check your calendar and start counting. 

 

Ice sheet at HTRC, 31 days and counting.

3. Temperatures – our 10 day forecast does not look good for trying to remove ice as day time high temperatures are forecast in the teens to low 20's with nighttime lows in the single digits.  Part of the concern with removing ice is exposing the turf to cold air temperatures after being insulated with snow and ice since mid-December.  In the past, some superintendents have removed ice and then recovered the greens with snow to provide insulation against cold temperatures. 

4. Physical ice removal – physical ice removal includes practices to fracture the ice with impact (hammers, chisels, aerifiers, slicers) and then remove the fractured ice sheet with shovels, tractors, or skid steers.  I recommend avoiding direct impact with tools such as hammers to less impact concentrated equipment such as slicers and aerifiers.  There’s always some risk associated with impact related ice removal but the alternative of leaving ice in place and rolling the dice on survival is also risky. 

 

Damage from a hammer used to crack ice.

5. Melting ice – there are many different products that have been used to melt ice including black sand, dark colored natural organic fertilizers, and synthetic fertilizers.  The key to any melting strategy is to be able to remove the water from the green following melting so it doesn’t refreeze and form another ice sheet. We will be testing products to melt ice at the HTRC in cooperation with researchers from the Univ. of Minnesota in the coming weeks.     

6. Labor – if you’re going to remove ice you need help.  Ice removal is not a 1-person job. If your golf course has 18 greens covered in ice even with several employees this is not a one day job. 

No Guarantees

Unfortunately there are no guarantees with respect to winterkill and whether or not ice is removed.  The days under ice cover for survival are estimates from research and conditions from course to course and even within the same course vary thereby effecting how long turf can survive under ice.  It’s already been a long hard winter and let’s all hope our turf survives so it’s not a long hard spring reestablishing grass. 

Grub Treatments with Nicotinoid Insecticides may Affect Bees

Dr. Dave Smitley

Department of Entomology

Michigan State University

There is a growing concern among entomologists and other agricultural scientists about the undesirable impacts of imidacloprid and other nicotinoid insecticides on the health of honey bee colonies, and native bees.  Nicotinoid insecticides are widely used on agricultural crops to control destructive insects.  They are also used on golf courses and home lawns to control white grubs and other turfgrass pests.  A recent study conducted in Kentucky by Dr. Dan Potter provides some useful information for how to avoid negative effects on bees that forage in treated lawns (http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0066375).  The results of this study can be summarized as follows:

1. Turf without any flowering weeds is not likely to be harmful to bees even immediately after a nicotinoid insecticide application because it is unlikely that bees will be present on the turfgrass.  Avoiding spray drift to surrounding flowering plants is advised.

2.  Applications of clothianidin (a nicotinoid insecticide used extensively on turfgrass) to turfgrass with clover in flower was harmful to bumble bee colonies foraging on the clover.   However, if the lawn was mowed just before or immediately after clothianidin was sprayed, so that there were no sprayed flowers present, there was no harmful effect on the bumble bee colonies.  Also, no harmful systemic effect was observed when the clover began to bloom again after clothianidin was applied, as long as the new flowers were not present when the lawn was sprayed.  In the discussion of these results Dr. Potter notes that more research is needed to address the long-term effects on bees throughout the growing season after the uptake and translocation of nicotinoid insecticides by clover and other flowering weeds.

 

White clover flowering in a low maintenance turf.

3. Chlorantraniliprole, a new turf insecticide with a different mode of action, did not have any harmful effects on the bumble bee colonies under any conditions. 

Considering recent research on the impact of imidacloprid on honey bees, and the results of the recent study summarized above, I recommend that if a lawn with weeds in flower needs to be treated for grubs, that the homeowner or lawn care professional mow the lawn immediately before spraying a nicotinoid insecticide, so that flowers are not present in the lawn at the time of application.  Please note this is approach is also in compliance with the precautionary statements on the pesticide labels which specify not to apply clothianidin, or other neonicotinoids, to blooming nectar-producing plants if bees are visiting the treatment area.  An alternative may be to use chlorantraniliprole which did not appear to be as harmful to bees in the Kentucky study.  Also, homeowners and lawn care professionals should follow three simple steps of MSU Smart Gardening to grow turf with a dense root system that is tolerant of grubs, so that no insecticide is needed:

1. Mow lawns at the highest cutting-height setting on your lawn mower

2. Use at least 2 lbs N per 1000 square feet per year

3. Water lawns during dry periods

Michigan Fertilizer Act Changes

Kevin W. Frank, Ph.D.
Michigan State University

On Jan. 1, 2012 phosphorus fertilizer applications to turfgrass in the state of Michigan were regulated according to Act 451 of 1994, Part 85 Fertilizers.  Basically the amendments to the fertilizer act restricted phosphorus fertilizer applications to turfgrass unless a soil test indicated need or for new establishment.  However, there were provisions that phosphorus fertilizer could be applied at 0.25 lbs. P/1000 sq. ft. if the source was a 'finished sewage sludge, organic manure, or a manipulated manure'.  This provision resulted in many questions and some confusion about which natural fertilizers fell within this category.  

On Tuesday, Nov. 5 Governor Snyder signed Public Act 151.  This Act made revisions to Act 451 and in particular to phosphorus applications to turfgrass.  The key addition was that the term 'natural fertilizer' was introduced into the language.  Natural fertilizer is defined as a substance composed only of natural organic, natural inorganic, or both types of fertilizer materials and natural fillers.  Public Act 151 has immediate effect, meaning today a person may apply biosolids, a natural fertilizer, or a manipulated manure to turf at a rate of not more than 0.25 lbs. P/1000 sq. ft./application.  The addition of the term natural fertilizer certainly expands the number of fertilizers containing phosphorus fertilizer that can be applied.  The key for the turf manager is understanding that the rate restriction of 0.25 lbs. P/1000 sq. ft./application is still in effect for these fertilizers so correct product calculations, calibration and application is critical to ensure applications don't exceed the 0.25 lb. P rate.  

 

Fall Broadleaf Weed Control

Dr. Kevin W. Frank
Assoc. Professor & Extension Turf Specialist

The summer of 2013 was one of the best in recent memory for growing turf and unfortunately also one of the best for growing broadleaf weeds.  The turf thrived with favorable temperatures and timely precipitation throughout much of the summer and so did broadleaf weeds.  Summer herbicide applications likely burned down the top-growth of many perennial broadleaf weeds but recently weeds such as white clover, dandelion, ground ivy, and black medic have magically reappeared.  

White clover in turf.

The challenge with the summer herbicide applications is that they are very effective at burning down top-growth but in some cases they are not effective at killing the entire plant.  In contrast, fall is the ideal time to control weeds because unlike the summer when weeds are focusing on top-growth, in the fall weeds are storing energy in their root system and are more susceptible to herbicide applications.  So if your turf has been overtaken by a bevy of broadleaf weeds, applying a herbicide in late September or early October will make a difference in what you battle next year.  Apply the herbicides on a sunny day when rain is not in the forecast for 24 hours.  We want the herbicides to dry on the leaf surfaces and not be immediately washed off.  There are many different herbicides that could be used including the most common three-way broadleaf weed control mixtures.  As with any pesticide application always make sure to wear the appropriate safety attire and follow all label recommendations.  As many have lamented over the years, the only shortcoming of fall broadleaf weed control is that you really don’t get to watch them die.  You generally won’t see the twisting, shriveling, and discoloration that often accompany herbicide applications but next spring the weeds will be gone or at least their numbers will be significantly reduced.

With fall herbicide applications we often miss the site of weeds dying.

Nematodes in Michigan?

Fred Warner
Nematologist
MSU Diagnostic Services

I once read a statement that some golf courses/country clubs spend up to $50,000 per year on fungicides. Obviously that figure implies there are some serious diseases of turf caused by fungi. But, what about nematodes? They too can cause serious problems but are often ignored. I’m often fond of saying, “Ignoring a problem won’t make it go away.” Nematodes are probably the cause of some symptoms observed on turf and are going undiagnosed. I base this assessment on the fact that until the past two or three years we typically received fewer than a dozen commercial turf samples per year in Diagnostic Services for nematode analyses. Things have changed as I think some superintendents now have me on speed dial.

Over the past few years, nematode problems appear to have become more prevalent on golf course greens in our region. The cause for this phenomenon is unknown but if I am to think out loud, I wonder if it has to do with a movement away from traditional insecticides used to control cutworms and other insects in turf to materials of different chemistries. Nematologists have observed this in corn as many growers have stopped using traditional insecticides for corn rootworm control in lieu of genetically modified, stacked, seed-treated corn hybrids. The organophosphates and carbamates used in the past probably helped to keep nematode numbers in check but with their discontinued use, nematode populations have had the opportunity to increase in densities. Could this be occurring in turf? Roughly 75% of all golf course samples processed in Diagnostic Services this year have contained high to severe numbers of plant-parasitic nematodes. At these levels, infected turf will exhibit symptoms that many superintendents say mimic those caused by summer patch. And if summer patch is suspected, my guess is nematode control is not objective number one.

Nematode feeding damage on a fairway in Michigan.

Cool-season turfgrass species are hosts to at least 10 genera of plant-parasitic nematodes. Typically, samples collected from greens and tees on golf courses contain at least three genera. In general, it appears, our turfgrasses tolerate nematode feeding fairly well. However, there have been situations in Michigan and our neighboring states where nematode feeding has resulted in serious symptoms. I’ve visited some greens where the turf has been thinned so severely that only sand exists especially after top dressing. One thing to keep in mind about the impact of nematodes is their feeding does not result in the production of any characteristic above-ground (secondary) symptoms. In controlled studies at MSU, the only quantitative effects nematodes had on the above-ground growth of creeping bentgrass were reductions in the numbers of tillers and leaves produced. The distribution of symptoms often gives a clue as to whether nematodes are involved. Nematodes tend to be aggregated in their distributions (especially cyst and root-knot nematodes), so the symptoms appear as patches. However, other soil-borne plant pathogens, especially fungi, can and often do have similar distributions.

The only way to properly diagnose nematode problems is to collect soil and plant tissue samples and send them to a nematode lab for analyses. To avoid problems, this should be done preferably in the spring. Roots of cool-season turf grasses grow most vigorously when soil temperatures are cool and due to this phenomenon, nematode numbers tend to rise as more feeding sites are available. To avoid problems, control tactics must be implemented at action threshold levels before nematodes reach damage thresholds. This is an important principle of pest control but is better understood for insects than nematodes. The key strategy is to keep population densities of pathogens and pests below levels where they are expected to cause damage.

One significant issue when learning of a plant-parasitic nematode problem in turf is the lack of chemical control options. Nemacur was an effective nematicide for use on creeping bentgrass greens but is no longer available. Other products exist but have not been evaluated in Michigan. Any organophosphates or carbamates should provide some control of nematodes but those marketed as insecticides will not be extremely effective. For example, nematode populations have been shown to rebound very quickly on greens where chlorpyrifos had been applied.

Typically, nematode control is not necessary on new greens and tees because sand mixes are used for their establishment and these materials should ideally be free (or nearly so) from nematodes. But, this is not always the case as some superintendents have experienced severe symptoms due to nematode feeding on newly established greens from contaminated sources. Usually, however, nematode numbers increase over time as they migrate from aprons, collars and fairways, from deeper in the soil or are transported on plugs from core cultivators.  New greens and tees should be sampled for nematodes roughly five years after establishment. Plant-parasitic nematodes are much easier to manage, or to alleviate symptoms of their feeding, if control tactics are implemented when their numbers are low. Early detection is important, remedies are limited.

Nematode damage on a fairway.

If you suspect you have a nematode problem, in addition to collecting a sample for a nematode analysis, I also suggest you also collect soil and grass clippings for nutritional analyses. Because chemical control options are limited, cultural controls are the first tactics to consider. If nematodes are recovered at levels below damage thresholds, then the evidence indicates they are not the causal organisms if symptoms are present. However, if high population densities are recovered, action should be taken to reduce their population densities or alleviate the symptoms they cause. What approach to take? Well, the soil and tissue samples will help to determine the course of action. If the soil and tissue results indicate less than adequate levels of nutrients, especially potassium, obviously an additional fertilizer application(s) is necessary. However, if the soil results indicate nutrients are above critical levels but tissue tests suggest otherwise, these results indicate root dysfunction. The nutrients are available in the soil based on the test result(s) but the roots are not capturing them, therefore the plants are growing poorly. What pathogens reduce root volumes and weights? Nematodes. Additional steps now need to be taken to improve plant health and this may involve reducing the population densities of plant-parasitic nematodes. However, proper fertilization, using synthetic or non-synthetic fertilizers, using a different watering program and aeration should go a long way toward alleviating the symptoms caused by nematode feeding. If nematodes are present, the most important concern is the health of the turf roots. Reducing nematode numbers may not be necessary. Implement any cultural tactics that improve root health. After all, is the owner or member of a country club going to be more interested in the numbers of plant-parasitic nematodes in the soil or that the greens appear healthy and look good?