Cottonwood trees are commonly found on golf courses, especially in floodplain areas and near waterways. However, a major issue that comes with cottonwood trees are the wispy, cotton-like puffs that surround and transport seeds and give the tree its name. This “cotton” can create various playability, presentation and maintenance issues and cleaning it up can be incredibly difficult, especially when there is any moisture on the ground from dew or rainfall.
Fortunately, growth regulators can be used to inhibit seed formation. Apply dikegulac sodium (Atrimmec) in a band around the trunk of the tree according to the labeled directions two to three weeks before bud swell in the early springtime, or after approximately 200 Growing Degree Days (GDD) at base 32 F have accumulated after January 1. The ideal timing for this application can occur much earlier than many anticipate. Applications in the Midwest should be made from late February to early March, well before it seems like winter has ended and the growing season begins. It is better to apply earlier in the GDD range than later, as the product is not typically metabolized in the plant during winter, so you won’t lose any benefit by being slightly ahead of schedule.
The amount of dikegulac sodium used per tree depends on the diameter at breast height (DBH), or the diameter of the tree at 4.5 feet off the ground. Applying 3 ounces of Atrimmec with 1 ounce of an organosilicone surfactant (like Pentra-Bark) in 1 gallon of water per foot of DBH is recommended on the Atrimmec label to reduce unwanted fruit and flower formation. The recommended method for bark-banding applications is to use a low-pressure sprayer like a backpack sprayer to spray the bark all the way around the tree from approximately 4.5 feet off the ground down to the root flares of the trunk. When dikegulac sodium is applied correctly, it can reduce seed populations greatly. At the course where I used this program, I observed around 85% control of cottonwood seeds.
Bark-banding dikegulac sodium can also be used to reduce other nuisance fruit and flower formation on golf course trees, like inhibiting maple samaras in high-impact areas like around putting greens. For more information about plant growth regulator use on nuisance tree fruit, seeds and flowers, reach out to your local USGA agronomist.
Central Region Agronomists:
Zach Nicoludis, regional director, Central Region – znicoludis@usga.org
Tom Gould, agronomist – tgould@usga.org