Pest Alert №6 — Anthracnose
My first sighting of a fungal disease called anthracnose, Colletotrichum cereale, occurred earlier this week. This is not an old friend. It’s the enemy of Poa annua or annual bluegrass. It is the primary reason Poa was sent on its way. Chicago golf courses began an intensive overhaul of her golf green surfaces beginning in the early 2000s. Timing is everything. The Penn A’s and Penn G’s were available. Our first dwarf creeping bentgrass varieties had entered the stage and were better able to handle lower mowing heights than say 1950’s Penncross. It didn’t happen overnight. Things like Penn A-1 Penn A-4, Penn G-2 were introduced following rigorous testing throughout the United States via NTEP (National Turfgrass Evaluation Program). Look it up
The good news for this particular (excellent) superintendent is the dominant component in his greens turned out to be creeping bentgrass and not Poa. Good news? Yes, creeping bentgrass has a level of resistance to anthracnose. In these instances I say something like, “Look, that anthracnose is doing a natural conversion for you. You are going to get more creeping bentgrass out of this.” If only it were that simple. Creeping bentgrass also is susceptible to anthracnose at times. In places like Atlanta, Georgia, certain creeping bentgrass biotypes can be severely impacted by anthracnose in greens. How do I know? Well that’s where I just came from.
Wilt Stress. Mitigation of plant stress is rule number one when trying to avoid anthracnose in golf greens. Wilt is the main trigger. Randy Kane is a number one expert on this fact. He taught me that. His tour of duty was 1985–2005 in Chicago. Respect wisdom. I do
Trained Staff. Midday hand-watering is the most valuable tool a superintendent has. Trained staff that do not over-water is critical too. Remember the other component is going to be creeping bentgrass and it doesn’t like it wet (aka Pythium root rot is always lurking). Three things you need to learn if you are a golf course superintendent that’s most critical? Water, water, water. Or better said, irrigation, irrigation, irrigation. Chicago’s growing season 2021 started record dry in April. Now we have transitioned from July to August. It is once again very dry. Just look at the landscape. Look at the lawn sprinklers running. Look how it has become the predominate story of this growing season. Dry
Fungicides. Major advances in the development of fungicides labeled for turfgrass use has occurred over the last decade. A single group, the SDHIs, grew from a single active ingredient flutalonil and today compromises possibly a dozen. Additionally, newer DMIs with broad-spectrum control are available in 2021. These new DMIs are developed with attention to our needs on greens. They can now deliver fungal suppression at lower use rates and also provide less PGR effect (growth regulation). Older DMIs are great, but can cause bronzing/phytotoxicity as well as widening of leaf blades.
Always rotate fungicide groups when addressing anthracnose. QoI chemistries may not work = resistance issues exist with this disease. Contact fungicides are an integral part of fungicide programs in turfgrass for resistance management.
Wetting Agents. Chemistries that can reduce localized dry spot will be helpful to reduce the likelihood of midday wilt stress. In other words, wetting agents will help to reduce a primary stressor of greens that drives this disease.
Equipment/Foot Traffic Wear. Be very aware as to how golfer wear occurs in concentrated areas on greens. Monitor and rotate pin positions and on/off access points to greens. We scout not only for disease. We also scout for stress. Or wear in this case. Scout!
