Early Season Dollar Spot Sprays
The pathogen must be active in order for the mycelium to absorb a fungicide. We know that Sclerotinia homoeocarpa grows when temperatures remain above 55F in the presence of ample moisture. If such conditions prevail in March (as they did in 2012), then early season sprays may help reduce dollar spot severity later in the season. If temperature and moisture conditions do not favor pathogen growth (as they did in 2010 and 2011), then the March application will have no effect.
Winter conditions in the lower Midwest have been quite favorable for pink snow mold (aka Microdochium blight). Springtime outbreaks on putting greens may require application of a remedial spray to limit disease spread, especially on sites with a history of the disease. Often, a single application of a tank mix that includes chlorothalonil, iprodione, and a DMI fungicide will be effective in suppressing existing infections and limiting spread.
Our research with springtime fungicides on bentgrass fairways has had mixed results. In most cases, fungicides applied to fairway height bentgrass after the outbreak is evident, did not hasten turf recovery. If you are inclined to try a “fairway clean-up” spray, do a simple experiment by setting out a check plot—where an area of the turf remains untreated. By comparing the check plot with the fungicide-treated areas, you will be able to evaluate the benefit of your fungicide spray.
Fungicide Notes: Secure (fluazinam)
Throughout the season, I will try to make a point of discussing new and/or interesting fungicides for turf disease control. The first is Secure (Syngenta) -- its active ingredient (fluazinam) was developed for crop disease control in the mid-1990s –but it is brand new to turf markets. Secure is a contact fungicide with a reportedly multi-site mode of action. Therefore, the risk of resistance is very low (although there is a report of resistance among populations of the Botrytis pathogen on rice). The major target turf disease is dollar spot, although there may be some efficacy against other diseases. Fluazinam’s multi-site inhibitor makes it very attractive as a component in fungicide programs that must deal with season-long dollar spot threats—especially where chlorothalonil limits are at issue.Rick Latin, Department of Botany and Plant Pathology, Purdue University