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Fusarium Spread and Spot Treating Questions

Last year I wrote a post about how my approaches has much more disease than the rest of my pesticide free areas of the course. I hypothesized that it could be due to the overlap of fertilizer applications.

This year I was very careful to keep the fertility on my approaches lean and avoid overlap and this is what I got.
I've seen worse
Compared to a typical fairway

There is an obvious difference in the amount of disease even though they are the same species mix of grass, same height of cut and receive the same fertilizer treatments. Tees, Fairways and Approaches are all completely pesticide free.

At the time of writing that post a fellow Superintendent, Jason Hooper, suggested that it could be due to all the traffic the approaches got. At the time I didn't really think traffic had anything to do with it. The problem was is that I was thinking about traffic all wrong. I thought that the traffic would cause the disease by stressing the turf and making it more susceptible which was not an issue in my experience. What I failed to realize is that fusarium is spread by traffic! This is a big difference.

The approaches are run over by fairway mowers, approach mowers, and greens mowers! All of these mowers drag the mycelium around and spread the infection. They get three times the mower traffic than anywhere else on the course and the disease is at least 3 times as bad! Duh

I have some questions.

  • What impact on disease would spot treating individual infection points have on overall disease rates? Would there be a decrease in overall fusarium levels if spot applied early. How would the costs and EIQ differ between spot applications and broadcast sprays?
  • Does the incidence of disease we are seeing have to do more with conditions or the amount of mower traffic? Does more mowing = more disease?
  • Is there a difference in disease spread with mowers vs rollers. The idea being that mowers open the plant up and deposit the fusarium on fresh wounds, Rollers do not. This could be why we see a reduction in fusarium on plots that are rolled daily and cut every other day. Here are my observations and those of OSU on rolling and fusarium. Maybe rolling has no effect on fusarium and it's the lack of cutting that is the difference? I do not see any disease spread from my approaches onto my greens which suggests that the disease is only spread on mowers and not on wheels or rollers. This might also be why I have seen little disease on my greens so far this winter as I have been using Primo Maxx through the winter. I have only cut the greens once in the past 57 days! Maybe this is the sole reason I have seen success with fusarium in the past!?!?
  • Does rolling before mowing make an impact? Does the roller crush the fluffy white mycelium reducing disease spread from mowers?
  • Why are some turf species more susceptible to fusarium than others? Does the shape and mechanics of the leaf blade and how it's cut have anything to do with it?
  • Is it the height of cut or the frequency of cut that impacts disease more?
Oh so many questions.

What I plan on doing going forward is to treat individual fusarium patches on the greens. I will treat spots with a contact fungicide on days that I roll so that hopefully there is little active disease on the greens when I mow.

Now I'm thinking of a sprayer that detects disease spots and and selectively sprays them with the boom. Case in point: I sprayed all active spots on greens today with 3ml of daconil. The total area was 1.5 square meters or .04% of the putting green surface. This is slightly below label rate. This cost $0.08. A broadcast spray would have cost $259. Time will tell if spot treating fusarium on greens is a viable strategy. If I go out every day how long will I be able to keep up before I am overwhelmed?

Of course infection will pop up everywhere. I just think that it is made much worse by mowers...Who knows? Do you? Let me know what you think.

Spot Treatment using a spray bottle. 1.5m2 treated at a
cost of $0.08
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