July Begins! Moderate Heat, Dollar Spot, Brown Patch, Root Rot, and Poa Research
The fourth of July landed on a Thursday and meant most could enjoy more leisure time than is usual. And the weather cooperated. Moderate summer temperatures (80s for highs) were experienced in Chicago. Best of all a return of peak summer heat isn’t in the forecast until mid-July. Nevertheless, high humidity has stayed in place and so it definitely feels like summer. Humidity is a good thing for growers because it lessens the overall ET (evapotranspiration) rate of plants and thus the likelihood of midday wilt stress. Overall, we are in a good spot as far as plant health goes. But one caveat has remained since our wet spring. It’s what you can’t see. It’s what’s beneath. It’s the fungus among us. If you hadn’t noticed, a root rot of creeping bentgrass called take-all patch was in the Scouting Report headlines all of June. Not good. As the best growers will always tell you, “It’s all about the roots.”. This is why we monitor and maintain soil moisture levels very carefully AND invest in extensive drainage.
In the landscape perennials are now at or are approaching peak growth. And there’s been a lot of that in 2024 (again it’s been a wet one). And we’ve enjoyed that along the way — an ornamental landscape that is lush, green, and floriferous is preferred. In other news, the activity (and sounds) of periodical cicadas finally disappeared. It was just as the entomologists had predicted. In Chicago, we won’t see brood XXIII (Northern Illinois Brood) for another 17 years. And central and southern Illinois won’t see brood XIX (Great Southern Brood) for another 13 years. We’re going to miss their insect roar? Until then, our annual 4th of July firework celebrations to commemorate American freedom will just have to do.
Weather
Illinois State Climatologist Summary for June
Chemical Control of Turfgrass Diseases 2024 (New)
Some really good news for turfgrass managers this week. A cornerstone of fungicide recommendations for turfgrass diseases was updated and published. The last update was 2020. The PDF guide is printable and represents the most current summary of current peer-reviewed research of fungicides. The CDGA Turfgrass Program helped out and contributed it’s most recent research from fungicide studies in 2022 and 2023.
The Introduction
“Turfgrasses under intensive management are often subject to outbreaks of infectious diseases. Diseases usually are most damaging when weather or cultural conditions favor the disease-causing agent but not plant growth and vigor. Cultural conditions that predispose turfgrass to diseases include close mowing, inadequate or excessive fertility, light or frequent irrigation, excessive thatch, poor drainage, and shade. Good turf management practices often greatly reduce the impact of disease by promoting healthy plants that are better able to resist infections. Even under good management, however, diseases sometimes cause excessive damage to highly managed turfgrasses. The proper use of fungicides in these instances, in conjunction with implementing best cultural management practices that promote quality turf, can be an important part of an overall disease-management program.”
The Authors
- Bruce B. Clarke (Emeritus), Department of Plant Biology, Rutgers University
- Paul Vincelli, Department of Plant Pathology, University of Kentucky
- Paul Koch, Department of Plant Pathology, University of Wisconsin-Madison
- Ming-Yi Chou, Department of Plant Biology, Rutgers University
Scouting for Disease — Dollar Spot (Clarireedia jacksonii)
Our most chronic disease of turfgrass is a foliar disease known as dollar spot. The months of May and June typically represent low to moderate disease pressure for dollar spot because nights typically cool into the 50s.In the past two weeks it has begun to increase in its severity. Actually, July is when we begin to see high disease pressure which will then last until October. It’s normal and something we have learned to expect. The combination of summer heat (warm nights in 60s-70s) and high humidity (regular rainfall) represent ideal conditions for dollar spot epidemics in the upper Midwest.
Part of how we know what is going on with dollar spot each year is through an extensive amount of fungicide research we conduct to prevent this disease. In Chicago, we are currently monitoring dollar spot development at two locations: North Shore Country Club in Glenview (north suburb) and at Bob Berry Sunshine Course in Lemont (south suburb).
Scouting for Disease — Take-All Patch (Gaeumannomyces avenae)
Soils with poor drainage are most conducive for TAP. Fairways have been hardest hit by take-all patch in 2024, but greens are not immune either. Brand new putting greens are very vulnerable in the first year or two of establishment. Under high disease pressure older greens can also suffer and this growing season with overly wet conditions in the spring has reminded us of that.
An especially wet spring (2024) will be problematic given a highly susceptible host is present (creeping bentgrass) on a majority of golf’s putting surfaces. Applications to prevent this disease are timed according to soil temperature thresholds (45–60 degrees at a 2-inch depth). In a wet, humid climate (Great Lakes Region) fungicides are needed in the spring and fall.
Poa Annua control in creeping bentgrass using Velocity PM (Poa Management). by Shehbaz Singh, MS
Introduction
This herbicide research is for an upcoming Nufarm turfgrass field day set for July at the Bob Berry Sunshine Course, Lemont, IL. Newer selective herbicides allow turfgrass managers to remove one species of grass from another species of grass. For example, Poa annua can now be removed from creeping bentgrass tees, fairways and greens with relative ease. Two examples include 1) Poa Cure by Moghu USA and 2) Velocity PM by Nufarm.
A program approach with multiple herbicide applications is required. It takes time. Research can help find the most efficacious (fastest) program that can remove Poa annua without causing injury to creeping bentgrass.
Materials and Methods
The study is being conducted as a non-randomized complete block design with 4 replications. The study is conducted on a ‘Penncross’ creeping bentgrass tee with 50-60% Poa annua contamination. All replicated plots for a particular treatment are grouped in one block for demonstration purposes except untreated. Untreated plots are grouped in two pairs at each end of the study area.
Objectives
- Evaluate Poa annua control
- Evaluate creeping bentgrass reestablishment
- Evaluate turfgrass quality
- Monitor any phytotoxicity to creeping bentgrass
Poa Annua Control
Applications of Velocity PM reduced Poa annua contamination in all three treatments. Best control used a low rate with a 5 application schedule with one application still due on July 8.
Visual Green Color and NDVI
Visual turf quality of Velocity PM treated plots decreased over time. Both visual green color data ratings and NDVI were also reduced. The primary cause was due to the selective death and removal of Poa annua. With the application of Velocity PM, Poa annua changed from healthy light green color to a yellowish-brown color.
Both ratings indicated the low rate 0.75 fl oz of Velocity PM provided a more gradual transition from Poa annua to creeping bentgrass than did the mid rate of 1.5 fl oz. Therefore, the low rate with five applications total would be preferred because that treatment was also most efficacious in Poa removal.
Final Image
“Bottlebrush buckeye is a handsome shrub that has memorable long fluffy white flower clusters in early July. It is useful as an understory planting in woodland gardens, as a specimen plant, or in a shrub border. The wonderful, coarse-textured, dark green compound leaves turn rich buttery yellow in the fall. This is a large shrub that tends to sucker and, over time, will grow twice as broad as it is high, so it should only be used in large-scale plantings.” For more from Morton Arboretum see Aesculus parviflora.
