Pest Alert №10 — Dollar Spot Development in Chicago (mild so far)

The growing season of 2021 is now entering a “shoulder season”. Hello fall. Days are shorter. Temperatures are cooler. And dollar spot (usually) takes off like a rocket. That hasn’t happened yet. Why? Well, look at your Midwest landscape. It’s pretty dry. And that has been the story of this year. Nothing has happened consistently. Wet, dry then wet. September is dry once again. Dry

Research on an ‘L-93’ creeping bentgrass fairway continues at North Shore Country Club in Glenview. It hasn’t gone exactly as planned, but we did see a peak following hot, humid conditions the end of August (when Chicago feels like Atlanta). And so peak dollar spot damage occurred on Sep 1.

Dollar spot is important because it is a chronic problem of creeping bentgrass. The older Penncross variety (introduced c. 1950s) actually had a good level of genetic resistance to this foliar fungal disease. Since that time we’ve seen a lot of improvements as newer creeping bentgrass varieties have been improved. One of the biggest improvements has been the selection of dollar spot resistant creeping bentgrass cultivars.

In the 1990’s a good one named L-93 was introduced (resistant to dollar spot). Also in the 1990’s another (a bad one) named Crenshaw was introduced (highly susceptible to dollar spot). Since that time continuous improvements have been occurring with regard to creeping bentgrass which have ultimately improved the game of golf from tee to green.

Image 1. Peak dollar spot development occurred following a hot, humid period in August. Nevertheless, dollar spot pressure remains mild to moderate (periods of intermittent drought all summer). Study site: L-93 creeping bentgrass fairway at North Shore Country Club, Glenview, IL. Settle, Sep 2, 2021

Figure 1. Dollar spot disease progression peaked on Sep 2, 2021. Visually, only untreated and PGR (plant growth regulator only) displayed unacceptable turfgrass quality (less than 6.0). Fungicide programs performing nicely.

Image 2. In creeping bentgrass, dollar spot infection centers initially look reddish in color. Settle, Sep 2, 2021

Image 3. Dollar spot eventually appears as necrotic, bleached-white infection centers. Settle, Sep 10, 2021

Image 4. Recovery from dollar spot has occurred during September due to overly dry conditions (lack of leaf wetness) and cooler temperatures (creeping bentgrass recovery). Settle, Sep 10, 2021

Reference. Settle, Fry, Tisserat. 2001. Dollar Spot and Brown Patch Fungicide Management Strategies in Four Creeping Bentgrass Cultivars. Crop Sci. http://cdgaturf.org/peer/scijourn/2001Dollarspot%26BrownpatchControlonBentgrassCropSci2001.pdf