Turf Maintenance practices during the COVID-19 pandemic

The spread of COVID-19 is having a tremendous impact on golf course maintenance across the country.  Many superintendents are operating with limited staff and facing resource constraints that could get worse over the coming weeks.  Some superintendents are also preparing for the possible suspension of all course maintenance for several weeks, or even longer. 

At present in Australia golf is allowed to be played in all states except Victoria.  Obviously in Victoria the implications for course maintenance staff will be different to other states due to the varying restrictions.

A few important points to consider are as follows:

The recovery cost associated with forgoing or reducing a particular maintenance program.

Due to loss of revenue at many clubs, reductions in various maintenance practices is inevitable to address immediate needs but it is important to consider the long term recovery costs.

While decisions about whether turf maintenance can proceed in a given area will be dictated by forces outside the turf managers control, it’s important for users to know that any prolonged stoppage in maintenance will mean a long road to recovery.  

For example, foregoing a hollow tine aeration program due to this practice being time and labour consuming could lead to excessive organic matter build-up which will exacerbate the problem requiring additional resources to fix later on.  A good alternative to manage the associated issues with excessive organic matter would be to perform solid-tine aeration given that there is less labour involved in the process but still improving drainage aeration and turf performance.

Heights of cut

You could look at raising cutting heights to a height of cut that were the norm 60 years ago or so.  These heights being approximately 4.5 mm to 5 mm for putting greens and 20mm to 25mm for fairways, approaches and tees.  These are basic guidelines and will vary depending on grass type, climate etc and would probably be applicable in situations where the facility is closed for play.

Another way to determine the maximum height of cut suitable for fine cut areas such as greens would be to think in terms of percentages.  For example, you could raise the greens cutting height by 20% to 30% which would mean raising the height from 3mm to 3.5 or 4mm.

Raising the mowing height reduces stress and improves plant health by increasing its ability to produce sugars because of the greater leaf area. 

Raising the height of cut by more than 30% will require gradual lowering of heights over several weeks when everything returns to normal.

It is very important to always abide by the 1/3 mowing rule to avoid root shortening and the associated stresses that occur when mowing off too much leaf in one go.  This is a general rule which applies to mowing all types of turf at all heights of cut. 

A big benefit of raising the mowing height is that it is easier to abide by the 1/3 mowing rule because the grass grows slower at a higher height of cut. According to Kreuser 2020 creeping bent grass or annual bluegrass mowed at 3.15 mm grows approximately 40% faster than the exact same grass mowed at 6.3mm. “We have also noticed from our clipping volume research that skipping mowing for a day or two reduced total growth rates. Employing both approaches will slow growth rate and sustain turfgrass health. Using these two approaches may also increase access to new hole locations that would have been unusable when green speeds are greater. This further distributes traffic and minimizes N requirements”. (Kreuser 2020)

In other research done by Kreuser it was found that tall fescue mown at either 50mm or 75mm grew at the same rate per day but the higher mowing height meant you could mow less regularly.  For example, turf maintained at 50mm would need to mowed when the canopy was 75” tall in order to stay within the parameters of the 1/3 mowing rule.  If the grass is maintained at 100mm”, then it would need to be mowed at 150mm.  Assuming the growth rate was 25mm per week, the turf maintained at 50mm would need to be mowed weekly while the turf maintained at 100mm would need to be mowed every two weeks.

The general principals outlined in the above research could be considered when maintaining venues such as sports fields where ryegrass is maintained and the fields are out of play indefinitely.

How to use plant growth regulators to best suppress growth and reduce mowing requirements?

Plant growth regulators (PGR’s) are essential tools to reduce the growth rate of turf and frequency of mowing.  Gibberellic Acid (GA) inhibiting PGR’s not only reduce clipping yield, but also promote a number of secondary benefits ranging from increased leaf colour and density to increased stress tolerance and reduced nutrient requirements. Incorporating a plant growth regulator (PGR) program into the maintenance schedule is crucial during these unprecedented times.

It is very important to understand the growing degrees day calculations to maximize the effectiveness of plant growth regulators (PGR’s).  Temperature affects the duration of plant growth regulators (PGR’s) while application rate affects the amount of suppression.  Applying at half the “normal” growing degree – day (GDD) interval leads to an accumulation of PGR within the plant tissue because the PGR is being applied faster than it is broken down or removed in clippings.  For further reading  growing degree day calculations  examines the theory of growing degrees-day and the modes of action of different PGR’s.

According to (Kreuser 2020)  “applying PGRs at high label rates, shorter-than-recommended growing degree - day intervals, or tank-mixing multiple products together can offer increased growth suppression compared to traditional PGR programs”.  Some examples of tank mixes that could be used include using Mode of action Group 3 DMI fungicides that have a growth regulatory affect tank mixed with Trinexapac -ethyl (Primo® Maxx) and Paclobutrazol (Trimmit® 2SC, Syngenta).  Consideration to uptake (ie foliar or root) needs to be taken into account when mixing PGR’s from different groups. Ie Group A PGR’s Trinexapac -ethyl is foliar uptake and the group B Paclobutrazol PGR is root uptake.  For more information it is recommended to read the article by Dr Bill Krueser  “Managing Growth Rate During COVID-19”  which is a great resource that discusses the ideal re-application intervals and tank mixes for the most commonly used PGRs.  The article is written in an American context but there is some useful information.

Also, Kreuser says that  “it’s difficult to predict if PGRs, even when applied with the various strategies just mentioned, will consistently allow putting greens to be left unmown for longer than three days and tees and fairways for longer than seven days”.
It is recognised that at facilities with a reduced maintenance staff, applying PGRs more frequently than normal or to playing surfaces outside of greens might prove to be difficult.

Also, it’s important to remember that you will get an increased clipping yield known as the rebound growth phase if you do not re-apply the PGR within the specific growing degrees day (GDD) interval.  Plant growth regulators can help to manage turf growth rates, but they need to be applied carefully and should be viewed as one of many tools to help manage turf growth.

There is the possibility of phytotoxicity when using PGR’s but this could be tolerated if traffic is low and there isn’t pressure to maintain a certain level of turfgrass quality.  It is worth noting that the risk of Plant Growth Regulator phytotoxicity is related more to clipping rate volume and turf species than the rate of application and the specific PGR. 

How much nitrogen?

Nitrogen inputs should always correlate to the amount of wear that the turf is subjected to.  With high usage and the subsequent wear Nitrogen rates need to match the recovery requirements to maintain a dense stand of turf.  During the current Covid-19 crisis where facilities are closed nitrogen inputs should be eliminated as there will be no wear.

“The soil nitrogen pool will be able to sustain the turfgrass until traffic levels increase later in the year.  With the challenges presented by COVID-19, withhold N fertilizer applications to avoid exacerbating mowing needs”. (Kreuser 2020)

 Also, in southern parts of Australia where soil temperatures are dropping and warm season grass growth is slowing down before entering dormancy there will be no requirement for Nitrogen.  Cool season grasses on the other hand will be growing slowly and require less nitrogen.  For facilities that are closed it is important to eliminate Nitrogen inputs, raise cutting heights and use PGR’s to reduce mowing requirements.

On the other hand, if your facility remains open for play but with a reduced staff all of the above still applies except Nitrogen rates to maintain recovery from wear should be maintained combined with a PGR program to control growth and reduce mowing requirements. 

In the warmer northern areas of Australia where warm season grasses prevail growth will slow down but the turf will not enter dormancy.  All of the before mentioned strategies would apply again with an emphasis on using PGR’s to reduce mowing requirements. 

Monitoring the growth rate and clipping volume is always valuable, especially now as management inputs are geared toward reducing the need to mow turf.

How to prioritise mowing of different rough areas?

In many cases the rough is the largest maintained turf area on a golf course, so these areas take the longest to mow.  Obviously reducing rough mowing frequency is recommended, but certain rough areas such as around greens should be prioritised.  For example, a rough area near a green could be mown every 7 to 10 days and a lower priority rough area every 14 days taking into consideration factors such as climate, grass species etc. 

By raising the mowing height, it will make it easier to increase the mowing interval for rough areas but a higher mowing height will likely lead to more difficult playing conditions and complaints.  Unfortunately, these issues may be something that can’t be avoided in the short term but obviously these changes to maintenance schedules must be communicated to the golfers.

Low rates of Glyphosate can be used to reduce growth in roughs although some susceptible grasses including Poa annua can be damaged and there will be a general yellowing of the turf.

What is the priority for managing weeds, diseases and insects?

Due to facilities operating with reduced staff numbers plant protectant applications for controlling weeds, diseases and insects need to be prioritised. Controlling diseases and insects should take precedence over controlling weeds.  There are options for controlling weeds later as weeds are typically not as destructive as diseases and insects.  If the budget and resources allow a preemergence application for winter weeds would be much more effective than postemergence applications later on in the season.


Normally playing conditions and turf health are equally important; but due to the fact that these are unprecedented times the focus needs to be adjusted to focus more on plant health rather than playability. 

What if the worst-case scenario occurs and there is a complete lockdown and turf facilities are unable to be maintained at all because turf management is not considered an essential service.

Look at the USGA greens section to see FAQ's regarding maintenance shutdowns. following link to see FAQ’s that the USGA greens section were hearing about regarding maintenance shutdowns.   

Click here to see all other resources that the USGA has put together


This article was writen by Steve Tucker, ASTMA agronomist. 

Click here to find further resources and support around the COVID-19 pandemic.



Kreuser B, PhD

March 26, 2020 by Greenkeeperapp 

Managing Growth Rate During COVID-19

What Happens If You Don't Maintain A Golf Course?
Featured Article | Green Section Record, Vol. 58, Special Edition | USGA, Published 3/27/2020