Opinion: Sycamore trees infected with fungus in Grand Junction, Colorado
Free Press Opinion Columnist
Recent cooler, rainy weather has been a welcome surprise for landscape plants and turf, with the exception of trees and most specifically the American sycamore. Sycamore Anthracnose is a fungal organism that attacks primarily American sycamore trees. The infection process is favored by relatively cool temperatures and prolonged periods of leaf wetness, both of which the Grand Valley has experienced throughout this spring; and we have seen signs of this disease in town. It causes a rapid wilt of newly emerging leaves. Larger leaves develop a brown growth along the main veins. Infected leaves often curl and eventually fall.
Anthracnose is most striking because of the defoliation (leaves falling off the tree) that can occur. Long-term damage is usually minor unless the disease occurs in successive years. The population of sycamore trees in Grand Junction is not a big one, but significant enough to be noticed. Some of the sycamores are very large trees. In the late 1960s and early 1970s the American sycamore was a popular tree planted in monocultures within some neighborhoods. When the Anthracnose disease was recognized as a threat, the American sycamore was no longer planted and cultural and chemical treatment programs were developed.
Chemical control of Anthracnose can be difficult and cost prohibitive. A wet spring needs to be predicted and a chemical application applied ahead of bud break. The chemical application should be repeated every seven to 14 days while environmental conditions are conducive to the spread of the disease. A healthy tree will produce a second set of leaves, which makes it important to have good cultural practices. Good cultural practices are the best protection that you can provide any tree. These practices involve getting water to the roots of the tree.
The rooting zone of a tree is found 12-18 inches below the surface. Given the dry winter and the bursts of heavy precipitation, water is not finding its way deep into the soil profile. Those of us who have not yet turned on our irrigation systems or are not providing winter watering are not getting the moisture we need to the roots of the tree. Trees have essentially been starved for adequate moisture for six month or longer.
The Grand Junction Forestry Advisory Board, the parks and recreation department, and the forestry division have been monitoring the weather conditions and the infestation of Anthracnose throughout city limits to determine the severity of the outbreak and if chemical control is warranted. The recent rainy cool weather has provided conditions for the disease to develop, but that same weather — rainy and windy — has prevented chemical control.
Forestry experts all agree: chemical control has been difficult and as the weather changes to hotter and drier, cultural practices are the best. Fertilizing your sycamore when you fertilize your lawn as well as additional watering throughout the summer is the best approach for the private homeowner. Trees located within city right-of-way that are the maintenance responsibility of the homeowner and of the city’s forestry division will continue to be monitored and if the prolonged rainy cold weather returns, appropriate steps will take place.
The bottom line is that some of these trees are probably going to become fairly unattractive this season as a result of this disease, but they should begin to bounce back by the fall. If weather returns to our typical patterns next spring, they should return to their normal appearance.
Randy Coleman is the forestry supervisor for the Grand Junction Department of Parks and Recreation Forestry Division. He is a Certified Arborist and began his forestry career with the city 15 years ago.
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