Novel Dollar Spot Control Programs

Dollar spot has really been the only challenge this year for golf course superintendents. With the recent economic downturn we are investigating ways to help superintendents reduce fungicide expenditures while maintaining quality playing surfaces. I have mentioned our dollar spot forecasting project, in collaboration with Dr. Damon Smith at Oklahoma State University, in previous posts. We are applying the preliminary model Dr. Smith developed in Oklahoma in our environment in Wisconsin. To date, the model has accurately predicted dollar spot development and making applications based on the model has resulted in 4 fungicide applications this year. When we compare efficacy to other fungicides either applied on 14-day intervals or 21-day intervals, the forecasting model holds up well. The one exception was a high pressure weekend and some dollar spot developed in the forecasting plots. The graph at the top left of this post depicts our results so far this year. The red arrows indicate when the model triggered and the blue arrows indicate when we made a fungicide application for just the forecasting plots.

The model did trigger before June 22 as a result we made a fungicide application on June 16th. Typical dollar spot programs in the Upper Midwest start on June 1, which would result in 7 applications when repeated every 14 days. For the 21 day treatments we have made 5 applications so far. Either case we can save either 1 or 3 applications per year. Currently we are putting numbers to these savings. We are using a municipal course, high-end public, mid-range private and an elite private course. Hopefully this will make are numbers relevant for a lot of turf managers. Please stay tuned because there is more to come!

Another project we are working on is expanding early-season dollar spot control. Basically we made a single early-season application and followed those applications up with 3/4 rates of Banner Maxx/Daconil every 21 days or full rates of Banner Maxx/Daconil every 28 days. Interestingly, full rates applied on 28 day intervals are providing the same level of control as our conventional program. We have not started our economic analysis of this project, but I know we have saved at least one fungicide application in this experiment. Again please stay tuned to this project too.

I am very excited about Lane's post yesterday! I saw the data with Civatas and I was excited, but we have not tested the product in the Upper Midwest. I know Dr. Derek Settle has, yet I cannot remember what he found. Civitas is scheduled in our snow mold trials this year, so we will see how it holds up. As always nice work Lane.

Megan's story about visiting with Aron Hogden is pretty funny. Poor Aron thought she was just a normal person coming over to lecture him about spraying. Aron had no idea that he peaked the interest of a turfgrass pathologist! Megan you are lucky you got out there without an inqusition from Aron.

Dollar Spot Forecasting

The weather is finally starting to warm up in the Midwest. I think we have turned the corner and left those nasty leaf spots behind us, hopefully. Now our attention turns to summer diseases. Dr. Derek Settle has seen foliar anthracnose on creeping bentgrass in Central Illinois and some pretty severe outbreaks of dollar spot in Central and Southern Illinois. Just this morning at the OJ Noer we saw small dollar spot infection centers on our Crenshaw fairway plots. The rest of the week's forecast is calling for mid 80's during the day and nighttime temperatures above 60 with high humidity. If you haven't made a fungicide application for dollar spot on fairways, you better do so this week.

I'm sure you can sense the excitement in my writing. I'm sure you are wondering why too. Well I was thinking that Wisconsin was not going to have a summer, but now I know that summer is on the way! I am excited because one of the projects we are doing in Wisconsin, in collaboration with Oklahoma State University, is developing a dollar spot forecasting model. Dr. Damon Smith initiated an experiment last year with the intent of modeling dollar spot development in the field. I was fortunate to see this experiment last year and Dr. Smith and I started to work together to pick apart the epidemiology of dollar spot. From his data last year, Dr. Smith determined that dollar spot will not develop until 5-day air temperatures reach or eclipse 57F and when relative humidity levels are above 70%. We have established plots with weather stations in Wisconsin to see if Dr. Smith's development data are similar to data collected in Wisconsin. He has constructed a preliminary model that we have begun to validate in Oklahoma and Wisconsin. Preliminary results indicate that the model accurately predicts dollar spot development in the field and therefore could help with timing fungicide applications targeting dollar spot.

During these tough economic times, a forecasting model for one of the most important turfgrass diseases will help to limit fungicide expenditures. Even saving a single application in areas that spray fairways will amount to a significant cost savings. Please stay tuned to see what unfolds with this project. In the meantime, my poor Cubbies could use some serious prayer time :)