Chlorosis has killed 15 maple trees in Colorado's Broomfield County Commons in the past three years.
Davey's Len Burkhart & Grant Jones
This nutrient deficiency prevents trees from creating enough chlorophyll and is common to non-native species in Colorado.
To help save future trees, Davey experts Len Burkhart and Grant Jones installed gravity jug systems to inject micronutrients into 32 maples trees on the grounds. The state of the maples and Davey's work was featured in Broomfield, Colo.'s Broomfield Enterprise and Boulder, Colo.'s Daily Camera.
Broomfield Searches for Maple-Saving Solution
by Joe Rubino, staff writer, Broomfield Enterprise & Daily Camera
Thirty-two maple trees on the grounds of Broomfield County Commons last week were made the subjects of a clinical experiment designed to find a treatment for chlorosis, a nutrient deficiency that has killed 15 trees at the Commons in the past three years.
Tom Wells, city forester since 1999, said chlorosis is a common affliction among non-native trees species in Colorado. The condition is brought on by a lack of sufficient nutrients, such as iron and manganese, in ground soil, and is common in Colorado because of the high acidity of native soil.
The nutrient shortage prevents a tree from creating enough chlorophyll -- the cells that give leaves their green pigment -- to perform photosynthesis, Wells said. Photosynthesis is the process by which trees use sunlight and water to produce energy, and trees without enough chlorophyll to perform the process eventually die, Wells said. Trees with white or yellowish leaves are likely suffering from chlorosis, Wells said.
"This is a problem throughout Broomfield," Wells said. "If you drive through any developments, you`ll see the yellow maples."
Wells said 15 young maple trees at Broomfield County Commons have died of chlorosis since 2008, costing the city a combined $7,275 for the original trees, their replacements and contracts with a tree company to plant and warranty the replacement trees for a year.
Wells, Jones and Burkhart visited the Commons last week to test seven experimental nutrient treatments on 32 maples at the park. The trees were divided in to eight groups, seven receiving various treatments for chlorosis, and the eighth group acting as a control, Wells said.
"All the trees are from the same source, planted at about the same time, so it should be a pretty good measure," Wells said. "(Chlorosis) is a problem across the Front Range, and if (Davey Tree) can figure out a cheap solution, it`ll be a win-win for all of us."
Six of the seven chlorosis treatments were applied last week, with the seventh to be applied in August. All of the treatments involve application of either a mixture of iron and manganese or a mixture of humate fertilizer and micronutrients. Application methods varied, with some treatments applied directly to the base of a tree`s trunk, while others were applied to the soil surrounding a tree`s root base, Jones and Burkhart said. They said they are looking for a combination of nutrient mixture and application method that is both cheap and effective.
"We`d like to find a product that will address maple chlorosis in Colorado," Jones said. "We did a little bit of a study in Fort Collins last year in a couple of commercial areas. There has been probably some slight improvement."
Two groups of maples at the Commons last week received trunk injections of iron and manganese mixtures. One group, easily identified by the big plastic jugs that hung from their trunks for two days, was given a mixture of iron and manganese sulfate through a gravity flow technique. A second group was given an injection of manganese using the speedier Arborjet system, which blasts the nutrients into the tree`s trunk at higher speed.
Jones and Burkhart said any improvement or progress in any of the trees won`t be known for a year to year and a half. The success of any treatment is contingent on many variables, including rainfall, the pH level of surrounding soils and other things, the scientists said.
Jones and Burkhart will attend to their final group of trees in August, when they use a macro-infusion trunk injection of Verdur iron and manganese on maples, before returning next spring to check in on results.
Wells said he is hopeful the maples in the Commons can be saved from chlorosis through the experimental treatments. The arborist said trees provide more to a community than just beautification through things such as catching excess rainfall and fighting carbon proliferation in the atmosphere.
Of the 15 maples killed by chlorosis in the Commons since 2008, Wells said he replaced half with Pink Sensation Box Elder Maples and the other half with Pacific Sunset Maples, both considered to be tougher species than those felled by chlorosis.