Anyway with the warmer drier weather comes the threat of Dollar Spot. The past two summers around the middle of July we got hit hard with dollar spot. It came overnight and it was very widespread and required a fungicide application to keep it under control.
This year we have changed our approach to managing for dollar spot in a number of ways.
Fertility: Last year we were on a brand name fertility program. While the turf looked good I wasn't too impressed with the overall health of the turf. It seemed that I was spraying more often than not and the turf was just sick. This year I completely redesigned my fertility program specifically for disease prevention. This summer my plan is simple. Light and frequent applications of urea through my sprayer. Urea is a readily available form of nitrogen and when applied in light doses you reduce the risk of leaching and volatizational losses. I feel that a GOOD constant supply of nitrogen is critical to managing dollar spot. What I have found is that N can almost be used as a fungicide for dollar spot control. Don't mess around with the snake oils, use what works. Urea works.
My fairways also got destroyed last season from dollar spot. The reason I think they were so badly infected was that my nitrogen source was sulphur coated urea (SCU). We typically applied it every two months but last June was extremely wet and most if not all of the SCU was released too quickly and therefore the turf was experiencing a nitrogen deficiency in July. This year we have switched to a 100% UMAXX product.. This product is a more stable slow release form of urea and so far has delivered outstanding results. Again, a slow consistent nitrogen feed is what I feel is key to managing dollar spot.
Cultural: It's no secret that I might roll a lot. My approach going into dollar spot season is to try and maintain the 2x daily lightweight rolling on my putting greens. Rolling has been shown to significantly reduce the incidence of the dollar spot fungus in a number of studies. They found that rolling increased the beneficial bacteria levels in the soil. These bacterial are not good news if you are dollar spot, fusarium, anthracnose, or pythium.
So far my management plan for dollar spot control is basically pesticide free. I have left a few areas on course to see if I can in fact control dollar spot without the use of pesticides whether it be synthetic or organic. Either way I don't like applying stuff if I don't have to.
While I am very confident in my dollar spot management plan I'm not 100% confident. For this reason I am using a few other tools to make sure I don't get nuked with disease this summer.
|Typical dollar spot infection in Poa annua.|
"Organic" Pesticides: I have decided to go with 3 different organic products this year just to see how they perform. I know that propiconazole works. There's no need to test that.
This year I am going to put out Civitas, Phosphites, and Rhapsody ASO. These three products show great potential and I am cautiously optimistic that they might just be the ticket.
The great thing I like about Civitas is its mode of action. It has no effect on the fungus but arms the plant's natural defenses for disease attack. This leaves little room for resistance issues and is very safe to use. It is a certified organic product. What I don't like about Civitas is the colour of the harmonizer. For this reason I am applying it at 1/4 rates every week to keep the offensively green colour to a minimum.
Potassium Phosphite is a regular part of my greens fertility program and should also help with any disease pressures that I might face this summer. I am still searching for a phosphite product that bears the Organic Materials Review Institute (OMRI) designation so if you know of one let me know.
A product that is completely new to me is Rhapsody ASO. The way I understand the product is that it is a bacteria that fights fungus. It is one of the same bacteria that's population is increased from lightweight rolling. I am planning on applying this product weekly in my tank mix for the next month or two depending on my control plot disease pressures.
I am of course going to leave some control plots to see if I can get away without applying these products as they are costly. And before you accuse me of going against my no preventative fungicide ideals consider this. I am leaving control plots to learn from my applications. I am also unfamiliar with these products and their efficacy. I want to see if I can make the "organic" option work. For this to happen I have to start "all in". From there I can learn and pull back after I better understand how effective these products work. Remember, this isn't propiconazole or chlorothalonil here.
And before everyone accuses me of being anti synthetic chemicals please understand this. I am doing this not because I feel that synthetic pesticides are bad. They are great effective tools for managing turf grass pests. I am simply curious and up for the challenge to see if I can make the newer alternative organic treatments work for me on my course. I am sharing this in hopes that others will also share their experiences and management tactics for the upcoming dollar spot season. Go ahead, hate me for it!