Park District of Highland Park issued the following announcement on Oct. 14.
This summer, we have experienced a sudden decline in the health of many trees in Sunset Woods Park. Trees that leafed out fully this Spring suddenly turned brown with dead leaves in the summer heat. Park District staff consulted with tree care consultants as well as the City of Highland Park’s Forestry Department to track down the cause. We identified a soil-borne fungus named Armillaria as a chief culprit. This fungus exists naturally in our soils. Our park trees normally are adapted to its presence. But its population increased with the extremely wet Spring. Trees, young and old, already stressed by the soggy soils were not able to cope.
Arborists have recently found that an application of phosphonates (a naturally occurring molecule related to phosphorus) has promise as an effective preventative treatment. It also has fertilizing benefits to promote better tree health. The Park District is taking pro-active steps to slow the spread of this condition in Sunset Woods and have treated vulnerable trees using a hand-held spray around the bark and root crown (where the tree meets the soil). This treatment may be repeated in Spring.
Trees most susceptible are located in areas where water tends to pond. There have been early signs of Armillaria conditions showing up in other areas in Lake County. In Sunset Woods, the trees affected include the White Oak, Sugar Maple, and Red Oak.
Trees such as Swamp White Oak are more adaptable to wet soil conditions.
Fortunately, many of the trees in the park are Swamp White Oaks that are tolerant of wet conditions. Also, the District has been proactive about planting new trees. For example, since 2015, Arbor Day volunteers have been planting 20 trees a year in the park. We will be adding more trees this fall, including species that are more tolerant of wet conditions such as Swamp White Oak, Ohio Buckeye and Hackberry.
Questions? Please contact Rebecca Grill, Natural Areas Manager, at 847-579-4087.
For more information about Armillaria click here.
Original source can be found here.
Source: Park District of Highland Park