Sunday, 9 December 2018

More Crazy Robot Mower Ideas

Recent discussions on twitter have drummed up a lot of interesting ideas about robots and a lot of hate too!

I love it!

For the haters or skeptics think about robot mowers like this.

Do you have an irrigation system with valve-in-head rotors? Do you have a central control? If yes, your biggest piece of equipment on your course is already a robot.

Afraid robot mowers will take away jobs? How did our current irrigation system technology affect jobs of people who used to manually plug in quick coupler heads all night long? Are you willing to go back to the way it used to be with irrigation? Didn't having actual people manually plugging heads in give it that personal touch that is lost with today's "automatic" sprinkler systems? Don't you think that the precision that modern irrigation systems bring makes golf better? Don't you think that trained and skilled people are still required to operate these highly efficient marvels of irrigation technology?

Just as it is seen today to be better to spend time fine tuning the irrigation system run times instead of spending time just simply turning them on and off again, the same will be true for robot mowers.

Did anyone imaging that we would one day be able to control thousands of sprinkler heads with extreme precision with a computer we hold in our hand?

I think the same big shakeup is coming to mowers sooner than everyone thinks.

Just like with our current irrigation systems, maximum efficiency is found with many heads that distribute water over a smaller area. The same will be true for robotic mowers. Instead of having 1 or two fairway mowers like we have today, we will have hundreds of small battery powered machines.

If one of them breaks down the rest of the "swarm" will be able to pick up the slack. Today, if your only current fairway mower breaks down, nothing gets cut until it is fixed., robotic or human powered.

One big mower is expensive. Many smaller mowers will be easier to start small with and expand their usefulness in small increments. There will be no need to go all in right away. As people are hesitant to adopt the new robotic technology. This will allow them to take baby steps

We won't have mowers that are dedicated to a specific area of the course. Instead, they will have variable heights of cut and will adjust as they enter different areas of the course. Think of the robots of being like a CNC machine today. They will roam the property at times that you specify and will adjust the HOC as needed depending on their current location.

Just like irrigation systems that are designed with a specific water window in mind. We will design these mowing systems with a mowing window. The number of robots that you require will be based off of the time you wish to spend mowing each day or night.

These mowers will change golf course architecture as well. How much of our current golf course design is based off of the needs of irrigation, drainage and mower capabilities? As mower capabilities change we can only expect the course designs to change as well.

Our current mowers have rigid heights of cut. Sure we can adjust them from day to day but they cannot generally be adjusted as we mow. This leaves course areas defined by the height at which the grass is cut. Greens are the shortest, Tees and approaches are a little higher, fairways are higher yet and finally there is the rough. Some courses even have intermediate rough and naturalized areas which aren't mowed at all.

Are rigid height of cut transitions because it's what's best for the game or because it's only what is possible with our current mower technology?
With robot mowers we won't need to define areas like this. We will be able to have soft transitions from one area to another. Focusing on technology that allows robots to mow super precise borders is nice but probably not needed except for maybe the edge of greens although Chambers Bay had no defined border on their greens for years. This feature is needlessly complicated and slows the progress of these mowers. It's probably not needed.

Course architects will be able to design holes with variable heights of cut depending on the weather or how difficult you want the course to play. Greenkeepers will be able to adjust the mowing patterns with the push of a button.

You will be able to upload any pattern of mowing that you want with ease.

After a while, just as we always seem to do. Nostalgia for the ways of old will come back into style and they will have to go through great effort to make mowers that create hard edges except it won't be hard. You will just push a button to present the course as it was back when they still used hickory shafts and mowers that could only cut one height of cut at a time.

We will be able to mount sensors and tools to these mowers as well.

They will drop seed and fertilizer on bare spots. They will spray weeds or kill them with lazers and target disease with UV light. This will drastically improve the environmental impact that golf courses have. No fossil fuels and highly targeted pest control using light.

Maybe this isn't realistic but the more I think of it the more excited I get about the possibilities that lie ahead.

While I really want to try out the current robot mower tech I don't think the leap from what they do today to what I have described above is that big. It would be neat to try out today's technology but we won't have to wait long for something vastly better.
Image result for husqvarna 450x
This is what the mower of the future will look like. Image:

Friday, 7 December 2018

The Future of Robot Mowers Today

In my travels I am very fortunate to be able to sit in on other people's presentations. While in Denmark last month I was able to sit in on a presentation by William Boogaarts who works for de Enk Groen & Golf in the Netherlands. They have been using robot mowers for years and in my opinion are way ahead of us in North America.

Yes, I know there are a few golf courses that use robot mowers already but they are very few and far between.

In his presentation he showed the impressive self driving mower tech that has been adapted to our current mowing equipment. While impressive, this wasn't what really caught my attention. Thinking that adapting our current mowers to be self driving is completely missing the boat when it comes to robotic mowers.

He showed us how they were using the small robotic mowers from Husqvarna to mow fairways. While not 100% ideal for golf courses currently, they are relatively cheap technology that can do the job TODAY!

The more I think about using these mowers on golf courses the more they make sense and the more I think how our current equipment manufacturers might completely miss the boat and end up like Kodak. Obsolete in only a few short years.

Currently these robotic mowers can mow up to 5000m^2 on a charge which is about 1 fairway. Their HOC only goes down to 20mm which isn't quite short enough for most courses. I think this could probably be modified to cut lower.

On fairways that were mowed with this mower, experienced greenkeepers couldn't tell the difference as far as quality of cut is concerned. These mowers are relentless and will mow as often as is required during the times of day or night that you specify. They can sense where the grass is longer and will return to these areas more often and will skip areas where growth isn't as much. In the near future this data could easily be used to adjust fertilizer rates based off of growth on your course. You could also add sensors to measure moisture and even a small seeder to drop seed on bare areas.

The best part and the thing that the current greens mowing robots can't do is, they require no human interaction to do their job. You just program them and let them go. They charge themselves and mow when needed. Set it and forget it.

Because we aren't paying a person to sit on these mowers we don't need to be concerned about the speed of mowing. They can mow all the time so we can get away with much smaller machines to do the work. This small size brings a lot of benefits to the job.

They don't wear the grass out as much as big mowers. Less wear and tear is a good thing. They can travel over softer areas without sinking and leaving deep ruts. They can also mow slopes up to 45 degrees! This is a big deal for us a Pender Harbour and if the grass is wet here on our 4th hole, we can only mow downhill even with all wheel drive mowers.

This increased turf quality isn't just anecdotal. This study showed that an autonomous mower modified to mow at 1.2cm had better quality grass

Steep slopes are a challenge for conventional mowers.
The best part I think about their small size is how they remove a lot of the mechanical complexity that the larger mowers require. No hydraulics, only 1 spinning blade. No fuel needs.

That brings up the point of transitioning to a sustainable energy use model on our courses. With large mowers their cost will only go up as the batteries are currently way too expensive for such large machines. If there's anything we don't need, is for our mowers to become more expensive. These small mowers can already be powered by battery today so the transition away from fossil fuels is easy and painless with small mowers.

There are downsides though. Because they are so small they can't mulch like our conventional mowers can. Leaves, branches pine cones and probably divots will need to be blown clear. For most of the year this isn't an issue but during the fall and winter storms this might cause issues.

Their docking stations need a power supply. If you have satellite irrigation controllers you could tie into their power supplies. If not it might be expensive to run power to each fairway.

The mowers today are only commercial or home owner specific. The leap to a golf course model is not that big. Maybe a bigger battery and a lower hoc and some sensors for moisture.

Drones will be obsolete as quickly as they became popular. There will be no need for them with these future mowers. I would not invest in drones today after seeing this. They are simply too difficult and costly to fly in some areas. Adding the sensor tech to the mowers bypasses all the issues with drone mounted tech.

Let's do some quick and dirty math to see how the return on investment might be for these mowers.

Cost of 1 current fairway mower. $60-90,000. every 5 years.

Cost to mow 10 ha of grass each season 3 times a week. $15-20,000.

Cost of fuel and mower maintenance each year. $5000+

So the cost of mowing fairways with this quick and dirty math is about $32,000 per year at best.

The robot mower with the highest capacity costs about $4500. You need 20 of these mowers to cut 10ha for a total cost of $90,000. Of course you need to supply power to your fairways but that's a one time cost and will vary a lot course to course.

So for the price of 1 fairway mower you can cut 18 holes of fairways but essentially will have no fuel cost or labor cost. You will have to spend some time cleaning debris off the fairways but that won't be significant. New blades every month or so also won't be a significant expense.

As you can see, the return on investment is about 3 years with these mowers today but you will potentially also get a better product with smaller machines. Many courses have more than 1 fairway mower so the ROI will be even quicker for them. With improvement in the tech it will be even less in short order.

It's crazy how quickly this technology is progressing. Just like other facets of the tech industry a lot of people will be caught off guard. This tech is ready today but with some tweaks it will be the best option for golf courses in every way. If you recently bought a new fairway mower, I expect it could be the last big mower you will buy. If you have an old unit that you are wanting to replace, look into this tech, the return on investment is very quick.

If this intrigues you, you can act today. These mowers are available everywhere, all they need are some forward thinking and innovative superintendents to try them out and make them work for golf.

I think I may have just purchased my last big expensive mower.

Wednesday, 17 October 2018

Out of Control Growth

It's totally true. This year I had big plans to control growth on my greens and boy did I fail. Despite having an intimate understanding of how fast each and every one of my greens was growing as well as how much fertilizer I had applied and how much growth I could expect from those applications, the growth rate this past May and August went completely off the rails. You'll also notice that the previous two years I was able to achieve relatively consistent growth, then it all fell apart. WTF!

As you can see, the growth this past May and August was significantly higher than in previous years.

This despite never applying less fertilizer to the greens. The total cost this year for those that are wondering came out to $275 for 1 acre of greens or about $0.07 per square meter.


Like Sean says, "we don't have as much control as we think we do."  Although growth this summer got away from me I have some suspicions why it might have been this way despite reintroducing growth regulators in July. The growth rates were so high that we struggled to cut enough grass each day and we were stuck with puffy conditions prone to scalping! Green speed was a challenge to maintain and we were forced to mow more than we would normally like.

Even with the elevated growth dollar spot was still a concern on a few greens. I think this is most likely due to the older bentgrass cultivars that remain on our greens. For the most part, dollar spot on the course was managed very successfully without pesticide interventions. Fairways and tees were in excellent shape all summer and didn't seem to experience the same growth explosion that the greens did.

We still have elevated organic matter from the winterkill episode of 2016. During the crazy heat we experienced this summer I bet the excess organic matter was mineralized and this led to extreme growth rates.

We started using Civitas again. Some of the product claims suggest reduced fertilizer requirements and increased growth. The first application was on the 16th of August, well into the big growth surge we were experiencing.

We started using primo again this year on July 9th and followed a strict 200 growing degree day reapplication interval helped out by my weather modeller.

As you can see, we had higher GDD this year than last so that certainly played a roll.

What else could it be?

The only other thing I can think of is grass type.

Last spring we were able to significantly increase the amount of bentgrass on our greens due to losing half of our poa thanks to winterkill.

The first green here is still mostly poa and you can see that despite it receiving higher amounts of fertilizer, it struggled to grow compared to our other bentgrass dominated greens.

It was very apparent to me this year that bentgrass grows much more with less fertilizer. Of course it could be less fertilizer or maybe the deeper rooted plant simply has access to more nutrients? There hasn't been roots deeper than 10cm for the past 20 years here so there is likely a treasure trove of nutrients in the depths below. Most plugs I sample have roots well below 20cm these days which essentially doubles the amount of nutrients available to the plant assuming it works that way.

Either way, I think the increase in clipping yield this year is partly due to having more bentgrass on the course and will allow me to potentially go even lower with fertilizer next season. Of course I will continue to monitor the growth rates and will adjust where possible despite having less control that I would like. I now also know what too much growth looks like and can really back off as we approach growth rates that can cause concern.

For more about these bitching graphs check out this post

Saturday, 25 August 2018

Lets try this organic thing again

When I told a local superintendent my intentions to try Civitas on my greens again he threatened to kick me in the nuts. Here's why and please note that this post does not contain any paid promotions although I am probably broke enough now to finally start selling out.

Hey, I also started a vlog, check it out here.

Back in 2012 I started using Civitas on my greens. It worked amazing. Back then only my 8th green was dominated by bentgrass and I went an entire year without any traditional pesticides on that green. Just mineral oil.

The only problem was that on a few of my shadier greens they turned to dirt and for the first time in my career I was forced to deal with winter kill.

Winter Kill of 2012 caused by a number of factors that mineral oil certainly didn't help. Shade much?
It turns out that when you apply oil to your greens every few weeks while the turf isn't growing and combine that with almost daily rolling of the greens that you will get dead grass.

Lesson leaned?



The following year I decided to try it again. I wrote about that here. Long story short, I couldn't see the true colour of the turf due to the pigment and was shocked to see the yellow grass after mowing the grass for the first time in a few weeks. I panicked, invited the local supers to come see only to have them call me an asshole for inviting them to see my perfectly healthy "dying" greens. They wanted to see carnage and all they got was good grass. I was just tricked into thinking they had suddenly taken a turn for the worse because I was used to seeing them nice and green from the pigment and not their true yellow winter colour.

I had a few jugs left over and I used them up without much thought in 2014 and since then I haven't' used the product because I couldn't find a benefit for its use.

During the time period from 2012-now my maintenance practices took a radical shift as this blog will clearly show if you go back to some older posts. All of the changes I made were to have healthier, lower maintenance grass that required the least amount of inputs to sustain quality playing surfaces (on greens at least). For the most part I was successful. In the past few years I have never used less pesticide as I learn how to best manage the diseases my course typically suffers from, dollar spot and fusarium patch.

With the exception of 2 of my greens, I have only applied 2 applications of a traditional pesticide this year. This is the best I have ever managed my greens. Of course some of it can be attributed to luck but for someone to find success who tries as hard as I do it makes you wonder if I'm actually on the right track.

I still have issues every now and then and need some outside help from pesticides to keep damage to a minimum.

Despite managing disease pretty good without pesticides, I still need some help

So why go back to Civitas?

There are a number of reasons why I have decided to try this product again and I doubt that the local superintendent will have to knock any sense into me this time.

It works. When I saw that I could go all year without traditional pesticides on my only bentgrass green it was amazing especially considering how bass ackwards my disease management strategy was back then. Now all my greens are mostly bentgrass so this gives me hope that maybe we can go all-in. I use almost no traditional pesticides anymore and only need a slight advantage to be successful. I have optimized the maintenance of our greens for disease management and think I might find success with what Civitas can offer.

Last year the impact of nitrogen was very apparent on my green collars. By treating collars with more nitrogen this year they are clean.

It's OMRI certified. I know what you're thinking and believe me, I'm thinking it too. I've even wrote about how dumb organic is. So why try to go the organic route?

Public perception is why. Maybe I'm wrong but I believe that there is a distinct advantage to be able to claim that all pest control is organic on a golf course. We all know that this isn't likely the case but as far as perception is concerned, organic is better than not organic and there's nothing you or I can do to change that. We see this all the time and it's a big deal. Take nuclear power. It's clean, emits no carbon, and no one wants it. Same goes for pesticides. They work, are miracles of modern science, but still, consumers don't want them.

So as far as my customers are concerned, Organic > not organic as long as I have quality playing surfaces and I think I can do that.

I have the tools to better assess plant health. Now that I measure the clipping yield on individual greens, I can see if certain greens are growing as expected. This "extra set of eyes" will help me even though I can't see the actual colour of the grass due to the horrid pigment colour that Civitas has. Seriously, it's a gross shade of green and I'm not a fan.

I also think that I can better manage the issues I had with traffic combined with Civitas during the winter. I have 2 possible solutions that will help reduce the potential for winter damage.

Apply it either on a GDD calendar or based off of clipping yield.

In the summer we average about 200GDD per week. The label suggests an application interval of about 14-30 days therefore if I use 400GDD as the target application interval that will give me about 14 days between applications in the summer months. In the winter that leaves me with an application interval of 3-10 weeks which is more reasonable for times of little to no growth. Overall this would require about 10 applications per year. I found success at the 0.250ml/100m^2 every 14 day application interval last time so this would require about 2.5L of product per 100m^2 per year which is well under the 7L maximum stated on the label.

The oil-o-meter on my HUD based off clipping yield

If I applied it based on clipping yield I could also increase intervals through the winter. If I applied it after every 250ml/m^2 of grass harvested that would also leave me requiring about 10 applications per year.

I think the GDD method is more useful during the summer but basing applications on clippings in the winter might be safer because even with low daily GDD in the winter, there is virtually no growth and I wouldn't want to start applying oil on top of oil. Either way, I will be comparing the two application strategies this winter to see what works best in practice.

I'm not really one to put so much faith in one product or one specific disease management strategie. It takes a broad spectrum of strategies to be successful so who knows, maybe I'll only use this product during specific stress periods.

I'm cautiously optimistic that maybe now this will all work. I barely need help compared to back in 2012. All I need is a little nudge to get me through a few tough times each year.

Fingers crossed.

Wednesday, 27 June 2018


This year I changed my approach to topdressing on my greens. I decided to use clipping volume to determine how much and when I would topdress the greens. The idea is that I will apply sand as the grass grows and hopefully eliminate layering from heavy, infrequent sand applications. My nifty HUD knows how much clippings I have removed from my greens and how much sand I have applied to them. It can then display the sand requirement in a way that makes sense to me.

Sand-O-Meter this morning before applying sand
Sand is applied

Sand-O-meter is automatically updated after I record my sand application into my online records.

I have always guessed at how much sand I need to apply which is a big problem. Sand is now the single most expensive input on my entire golf course and I only apply it on greens! ($2000 in previous years with a target of $500 this year) Just like I was guessing how much I aerify, I decided that if I wanted to refine my sand application practices (and be able to adjust them each year in a meaningful way,) I needed to do better.

Just like with fertilizer, water, and pesticides, no two years are the same for their requirements on your golf course. Using dates on a calendar to schedule maintenance practice such as these just doesn't make sense because Mother Nature doesn't give a shit what day of the month is it. If we want to refine things, we need to base our practices on the actual observed conditions.

a light blow and turn of the heads and they are looking good!
What makes sense to me to base topdressing requirements on is how much growth we have. More growth equals more organic matter production right? I mean, it's probably more complicated than that but in general terms that's kind of how it works.

So after over 6 seasons of collecting and measuring clippings on my greens I have a pretty good idea of how much grass I will harvest. I also have a pretty good idea of how much sand I used to apply.

This is where it gets a bit experimental for me. I'm hoping to reduce thatch accumulation on my greens through careful monitoring of nutrients added vs removed and in theory I hope to keep organic matter production to a minimum but who the hell knows eh?

So, I picked a number that is a lot lower than I have previously applied and will adapt from there. I'm hoping to not have to aerify much or at all so that amount of sand was removed from my numbers. If my chosen annual rate of sand per unit volume of clippings is a bit low, I can adjust it up and if it's a bit high I can adjust it down. In a year where I grow more grass I will automatically apply more sand and in years where there is limited growth I will apply less. Awesome! After a few years I should come to a good number for my course.

The math is simple.

I am applying 227g sand/m^2 per 1g Nitrogen/m^2 removed via clippings. Why this number? I guessed and will adjust it based on soil tests and physical greens properties tests.

To make it more user friendly for me and my staff I converted grams of sand/m^2 into a unit I call "tractor scoops". This is how many scoops are required from the tractor to apply that amount of sand. One hopper in our topdresser holds 2 scoops. Typically a light dusting here will require 4 scoops or 2 hoppers to do. This is an amount that I can apply any day of the week with minimal disruption to golfers but also won't result in me having to apply sand more than once every 3-4 weeks throughout the growing season.

To determine the mass of a scoop of sand you need to first take a scoop of sand with your tractor. Fill a pail with sand and dry the shit out of that sand. Then measure the mass of that pail of sand.

Then see how many pails of sand 1 scoop of your tractor can fill. This entire process took me a half hour. Hint: a tiger torch and a concrete mixer work great for drying sand.

Now you know how much a tractor scoop of dried sand weighs. You also know the volume because you know the volume of that pail right?

For me, one scoop of sand weighs approximately 360 kg when dry.

It is also 228,000 cm^3

1 scoop of sand on 1000m^2 is about 0.23mm thick of sand.

So at the end of the season I will be able to see if that 227g of sand per g of nitrogen removed from clippings is enough and can fine tune my sand applications from there. The ultimate goal is to use as little sand as possible because, hey, it's a non-renewable resource.

Tuesday, 26 June 2018

Growth Rate and Plant Health Hypothetically speaking....

Place looks better in late June that it did in May. Gotta love Junuary!
In my last post I wondered if I could use indicator species to help me grow my grass at the right rate. This is only a hypothesis but is what I have been trying for the past few seasons and it seems to work from what I've seen. Either way, It's not fact and could be total bullshit.

I wonder through, hypothetically speaking, if grass is healthiest (has the least amount of disease) when it's growing at the appropriate speed for the climatic conditions, what are the consequences of, say, using preventative fungicides and growing the grass at the less than optimal rate? (because hypothetically speaking the only way to truly grow the grass at the right speed is by not applying preventative fungicides and seeing the disease)

The more I think about it (if my thinking and observations are true) the only real way to truly achieve the optimal growth rate for plant health (again, less disease) is to use the actual diseases to help you fine tune things. So if this is true (not likely) then what kinds of other issues are we going to get if we mask the diseases with regular fungicide applications?

I'm building hypothesis on top of hypothesis here so this is so far fetched it's not even funny.

Also understand that what I'm trying here is to grow grass without any fungicides, organic or synthetic because I'm not convinced organic is any better than other ways of managing turf. It's all shit! (just kidding)

Is this (sub-optimal growth rate) one of the reasons some people experience major disease outbreaks as the previously applied fungicide wears off?

I know that's probably what I used to observe back when I used a lot of fungicide and had poorly timed fertilizer applications. I applied most of my nitrogen in the spring and fall as the "classic" cool season growth curve suggested I do. I was growing my grass the fastest when my fusarium and growth potential curve were suggesting I grow it slower. In the summer months I was growing the grass slowly when the dollar spot and growth potential curve were suggesting I grow it faster (for my climate anyway). It's no wonder I would get absolutely hammered with disease when I managed my turf this way. I was chasing my tail and putting out fires left and right! Maybe it's not directly a result of the fungicide killing of beneficial organisms as some would suggest, but a combination of that and grass that is growing at the wrong rate. Who the hell knows eh?

The 8th green is growing too slow and has the most dollar spot so I have it some extra nitrogen today.
Dollar spot on the 8th. Interesting how it seems to be on the margin of the bentgrass patch.
It's also no wonder why we had so much poa on our greens because we were constantly killing our grass and the only thing that was saving our ass was the constant supply of poa seed.

What about thatch? Thatch relies on the soil microorganisms to break it down otherwise we are left to physically dilute or remove it through mechanical means. If we are matching growth rates to the soil/plant biology then perhaps we can eliminate or reduce the inevitable organic matter buildup in our soils?

What about plant health in general? The plants ability to be healthy and tolerate traffic and stay nice and dense and competitive? Lucky for me most of our traffic comes at times of the year where growth rates are the highest. It's almost like the ideal conditions for golf are also the ideal conditions for grass growth.

Of course there are going to be times when you need to grow the grass at a rate that will make disease worse. Clubs with high amounts of traffic in the winter months where the grass hardly grows and courses that absolutely need slow growing grass for tournaments in the summer months. I don't think there's any getting around those situations but thankfully most lower end clubs don't have those pressures.

Boy would I love to see some solid research on this.

Clearly I've been thinking too hard.

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We have never done less or spent less on our greens

Monday, 25 June 2018

Using indicator species to fine tune fertilizer applications

I get it. I talk a lot about turf disease and fertilizer but it is only because I think that the two things are closely related. More specifically, I think the amount and types of diseases on our grass are closely related to how fast the grass is growing.

Not too shabby
From what I have seen over the past few years of intense growth rate monitoring and reduction in fungicide use is that if we can grow that grass at the right rate, we can reduce the amount of disease significantly.

The trouble is that it isn't that easy to figure out what is the right speed. Further complicating matters is that if you add too much fertilizer, you cannot take it back and are stuck with grass that is either growing too fast which can lead to all sorts of issues at certain times of the year.

I have used the Growth Potential mathematical model to predict nitrogen needs, clipping volume and many other things to try and help me get it right and each year that I further refine my fertilizer timing and rates, the less disease issues I have.

One of the first strategies that I used when starting to really try and reduce my reliance on fungicides was to simply not apply preventative fungicides and use my observations to try and figure out why my grass was diseased. I could never understand why some areas were covered in disease and others were untouched. It started with obvious things like sunlight, drainage and disease spread but then focused on how fast my grass was growing. Grow it too fast and it gets disease, grow it too slow and it gets disease. Grow it just right and there is little or no disease. It sounds too good to be true and it might just be. We have to maintain playing surfaces after all and we can't just grow our grass at speeds to reduce disease. We need to grow it at speeds to manage wear and tear etc.

On a deeper level I think this all ties together with the soil microbiome and that thing called balance we all seek to achieve.

Growing the grass at the right speed isn't that easy because the right speed changes every day! How can we consistently hit this moving target? The mathematical formulas can help but they aren't perfect.

What if I go back to my first disease management strategy and let the disease tell me how much I should fertilize my grass and when and combine these observations with the data collection and growth potential model?

I think it might just work and if you have read some of my recent posts you will know where I'm going with this.

Here are a few of the common turf diseases I deal with and how they can help you refine your fertilizer (and cultural) program and hit that sweet spot with more consistency.

You can further refine things if you fertilize greens individually based on their growth rates and disease levels like I have done for the past year. It's not that hard to do either. Fill up your tank with water with enough to spray all greens. Add the stuff you need to apply to all greens like wetting agents etc. Go spray the greens that don't need any fertilizer. Add some fertilizer. Go spray the greens that need some fertilizer. Add more fertilizer. Go spray the greens that need even more fertilizer.


This disease is mostly a problem in the winter months but I have seen it every month of the year! To me it indicates that the grass is growing too quickly and no additional fertilizer is needed (unless damage is widespread and you need to fill in the dead spots with the aid of a fungicide).

I have noticed that the Smith-Kerns dollar spot model does work for fusarium at some times of the year but I eagerly await the upcoming release of a fusarium specific prediction model to make managing this disease and my plant growth rates that much easier.

Fusarium in June! With elevated growth rates and a brief cool and wet week the disease popped up. Luckily it dried up and warmed up and it went away.

Dollar Spot

This disease is only an issue here in the summer and only on the slowly growing greens. To me dollar spot indicates that the grass is growing too slowly for the conditions and more nitrogen is needed.

The Smith-Kerns dollar spot model is awesome and when I see disease pressure spike I check my clipping volume data to ensure my grass is growing fast enough.

A light spike in disease pressure saw some disease on our greens.

I find that a growth rate of 20ml/m^2 per day is sufficient to manage dollar spot in most cases.


This disease has only become a problem on my greens in recent years I have have consistently reduced my annual nitrogen rates each and every year since 2012. This disease indicates that the grass is growing too slowly and more nitrogen is needed unless you are a sick bastard like me who likes to see the poa die. On our predominantly bentgrass greens I don't adjust the growth rate and just let the poa die.

anthracnose on my first green
As can be seen on the lower chart, my first green has been growing slower than most while receiving the most nitrogen fertilizer to help manage anthracnose on that green.

While still obviously infected (great time to drop some seed), the green is still alive with the additional nitrogen treatments. 


This disease is only an issue in wet summers or if I get lazy and overwater the greens. Dry them out and incorporate some 21-0-0 into your nitrogen fertilizer treatments and it should go away. Needless to say, I haven't seen this disease in years since I stopped being so lazy and started using more 21-0-0.

Brown Patch

This disease used to be a big problem on our greens but we haven't seen it since we stopped watering in the afternoons. Let you grass be dry for as long as possible to keep the humidity down during the heat of the day.


Not a disease but a great indicator species as well. In 2012 our fairways were thatching, soft and didn't drain very well. I decided to try and use less nitrogen to see if we could do something about the thatch. Each and every year I applied less and less fertilizer and the fairways improved more and more until this year when the weeds took over.

What I think happened is that we finally burned up the excess organic matter and now the grass isn't getting enough nitrogen to compete with the weeds. This is a great indication (along with the fantastic drainage and firm conditions) that I need to fertilize my fairways slightly more if I want to keep weeds to a minimum without the need for a herbicide. Even then, the fairways will always be the weakest part of the course until we can renovate them to smooth out the settling that has occurred over the past 30 years.

So while we have a lot of high tech tools available to help us make decisions I think that we can also use turf diseases to do similar things. The diseases are reality and the models are just theory. Ideally we want to prevent the disease in the first place so I still think the high tech tools are essential for keeping things balanced and understanding why the disease is an issue and how you can take action to correct it before it becomes a costly issue. We can use the growth potential model and clipping volume data to get into teh ballpark then if we pay close attention to these diseases (assuming you don't apply preventative fungicides) we should be able to adjust our maintenance practices to hit the sweet spot. And about that playability thing....for me at least, they two things are also closely related. Healthy grass = good surfaces for golf!

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