Investigate dew removal and biocontrol on different creeping bentgrass cultivars for the control of dollar spot

BY J. M. VARGAS JR. AND NANCY DYKEMA PSM DEPARTMENT, MSU

How the MTF funding will be used to support project:

The MTF funds will be used for technical and undergraduate support for setting up and running the research trial including making biocontrol and dew removal applications, maintaining study site, rating plots, and data analysis and report-writing, among other tasks.

Expected Results and Methods:

Obviously, we have known for years that dew removal will reduce dollar spot, but does it work the best on susceptible or on resistant cultivars? Is there any benefit afforded by removing dew from a resistant cultivar? Biocontrols have been tested for many years with little success, but will they work on intermediate cultivars or highly resistant cultivars? Learning more information about these interactions could help reduce fungicide inputs for the control of dollar spot. We propose to examine the impact of creeping bentgrass cultivar (CBG) including a susceptible cultivar, Penncross, an intermediate cultivar, Shark, and highly resistant cultivar, Coho, in combination with dew removal and a biocontrol on the development of dollar spot. Techniques to control dollar spot, the most costly disease on golf courses from a management perspective, have been studied at length, but there are still many questions which need to be addressed in order to develop more consistent, economical management strategies.

Methods:

The study will be set up with three replications of each treatment. The study site has been seeded to large plots of Coho, Shark and Penncross creeping bentgrass. Dew will be removed on a frequent, consistent basis in the plots. Biocontrol treatment applications will be made at 48 GPA or 96 GPA using a CO2-powered backpack sprayer. Fertility will be applied as needed. The study site will be inoculated with a sand-cornmeal mixture infested with the disease pathogen. Treatment applications will be made according to label standards. Plots will be rated visually for percent plot area blighted by disease and for turfgrass quality. Photos will be taken periodically during the trial.

Treatments to be tested in this trial include combinations of CBG cultivars, dew removal and biocontrol application as follows:

1 Coho; No Dew Removal, No Biocontrol

2 Coho; No Dew Removal, Biocontrol

3 Coho; Dew Removed, No Biocontrol

4 Coho; Dew Removed, Biocontrol

5 Shark; No Dew Removal, No Biocontrol

6 Shark; No Dew Removal, Biocontrol

7 Shark; Dew Removed, No Biocontrol

8 Shark; Dew Removed, Biocontrol

9 Penncross; No Dew Removal, No Biocontrol

10 Penncross; No Dew Removal, Biocontrol

11 Penncross; Dew Removed, No Biocontrol

12 Penncross; Dew Removed, Biocontrol

Expected results.

We expect to determine whether cultivar resistance, dew removal and biocontrol treatment applications combined confer industry-accepted levels of dollar spot control.

Specifically, upon completion of this trial, we expect to determine whether:

1. there are any benefits to removing dew from intermediate or highly resistant CBG cultivars.

2. biocontrols are efficacious against dollar spot when used with intermediate or highly susceptible CBG cultivars.

Grad Student(s) Involved. None

Benefit Group: Golf course superintendents and other golf turf managers.

Estimated project duration: four seasons, although funding request is for one season

Dollar spot (DS) pressure was moderate to high in this trial in 2022. The disease increased rapidly in August; however, due to seeding rate, timing, germination, and fertility, annual bluegrass (Poa annua) contamination was rampant in the study. This made DS ratings less reliable regarding the cultivar factor. Overall data for 2022 suggests treatments with Coho CBG had the lowest amounts of DS compared with Shark and Penncross. In mid-August, Coho with Zio and dew removed resulted in significantly less DS than all treatments on Shark or Penncross cultivars. Disease ratings ceased after sustained flooding on the plots lead to clipping deposition on areas of the study site which eliminated differences in DS levels. By the end of the trial, subplots plots within each cultivar whole plot were difficult to distinguish. Turfgrass quality ratings followed similar trends as DS levels. In general, Coho cultivar treatments yielded the overall highest mean quality ratings. Turfgrass density/ grow in affected quality ratings early in the season, particularly on the Shark and Penncross cultivar plots. Later in the season, quality was affected by DS levels. In general, quality ratings on the entire study throughout the trial period were below industry-accepted standards.

For the 2023 season, Polyon fertilizer will be applied as in 2022, however, supplemental fertility will be added as needed to maintain adequate turfgrass quality on at least some of the plots. Additionally, treat for ABG. Zio and dew removal treatments will be applied as in 2022, with applications beginning in June.