Des Plaines Park District fights to save ash trees
After attending a Metropolitan Mayoral Caucus for EAB management in 2011, Steve Krotz, Landscape Maintenance Supervisor for the Des Plaines Park District, determined the best treatment for the Park District Ash trees emerald Ash Borer infestation was a systemic insecticide injected into the trunk at the base of the tree.
“Trees give you a sense of connection to the past and a sense of community in a neighborhood.” Steve Krotz, Landscape Maintenance Supervisor, Des Plaines Park District
The same way our children grow and mature season to season, so, too, do our neighborhood trees. While offering us shade, reducing cooling costs, and helping to prevent erosion, trees add an intrinsic value to our private and public properties. Across their more than fifty parks and open green spaces, the Des Plaines Park District maintains over 3,500 trees. The plantings are diversified, and many of the trees are native to Illinois. Approximately 20% of the population is a combination of green and white ash trees.
Over the past several years, ash trees have been under attack from the Emerald Ash Borer, Agrilus planipennis. The EAB was first detected in Illinois in 2006, and the first confirmed infestation in Des Plaines was on January 27, 2010 in the forest preserves at Devon and River Roads. The borer is an exotic, dark, metallic-green beetle native to Asia, which was accidentally introduced into the United State in the 1990's. It has since spread to trees in over 14 states, causing an estimated 3.5 billion dollars worth of damage every year. While it prefers the green and black ash, it will also attack the white ash, making it a threat to the entire Faxinus genus.
The Emerald Ash Borer has no natural predator to keep its population in check. It preys on three to four year old trees with soft tissue, disrupting the vascular system and preventing the flow of water and nutrients until the tree literally starves. The female lays up to 100 eggs, depositing them on the bark of the Ash along the trunk and major supporting branches. Newly hatched larva bore through the bark to the phloem—the living tissue that carries the organic nutrients, particularly sucrose, to all parts of the tree where they are needed during photosynthesis. The EAB feed on the sapwood until the weather gets too cold in the fall. As they feed, the larvae create long serpentine galleries which enlarge in width as they grow. To emerge from ash trees, adults chew D-shaped exit holes through the bark and are then capable of immediate flight. The adults fly up into the Ash's canopy and feed on its leaves, doing even more damage to the tree.
Typically, it is in the third year of a tree's original infestation that it develops dieback in the canopy. The canopy of a tree, especially those in large, mature trees, captures CO2 and pollutant particles in the air, reduces storm water run-off, and creates large shade areas, reducing cooling costs. The Park District has many Ash trees lining the drive into the Leisure Center. These ornamental trees have a deep green waxy leaf that changes to yellow, orange, and deep red in the fall. In 2010, a bark window was cut into an Ash tree on the east side of the Leisure Center to determine whether these trees were at risk. A positive confirmation was made when the serpentine galleries were revealed.
The treatment approach for the Department of Agriculture, and most public agencies with affected populations, has been to clear-cut any Ash tree infected by the Emerald Ash Borer. In Des Plaines, dozens of Ash trees on city-owned parkways and land have been removed to contain the pandemic. At the Des Plaines Park District, Steve Krotz, their Landscape Maintenance Supervisor since 1991, opted to try another approach. He took a look at the Park District's tree inventory. A small percentage of older Ash trees, especially those planted in parking lots, were under stress due to root confinement and early EAB infestation. Those trees were removed, to contain the infestation, but also to make way for new safety lighting and security cameras. Krotz then decided to try to save the rest of the District's Ash trees through treatment.
After attending a Metropolitan Mayoral Caucus for EAB management in 2011, Krotz determined the best treatment for the Park District Ash trees was a systemic insecticide injected into the trunk at the base of the tree. The active ingredient in the insecticide is Imidaclorprid, which, once injected, is absorbed and translocated through the trunk stem to the branches. Imidaclorprid acts as an insect neurotoxin, resulting first in the insect's paralysis and eventual death. It is a non-restricted fertilizer, which is part of the Park District's mandate, and is selectively more toxic to insects than mammals. The treatment, applied annually during the period from mid-April through June, takes four to six weeks to be distributed throughout the tree, and the insecticide not only kills the adults, preventing them from foraging for leaves, but also kills the grubs within the vascular system. Krotz is also working to maintain the health of the Ash trees by pruning, creating optimum soil conditions, and providing superficial feeding. “My feeling is if we can slow down the borers' population within the tree, the tree's health will improve so that it can recover and continue to grow,” Krotz said. He has treated 156 Ash trees to date.
In 2012, The Des Plaines Park District applied for, and received, a Metropolitan Mayoral Caucus Grant, which is administered through the Morton Arboretum. Those grant funds, totaling $10,312, were used to cover the cost of an inventory of the tree population across the District; the creation of a GPS mapping component, accessible on the Des Plaines Park District website, that also includes the location and species of each of the trees in the Tree of Life Program; and the development of the District's EAB management program.
In the long run, managing the EAB problem is more cost effective than removing and replanting new trees. Outside contractors are required to remove infested trees and properly dispose of the wood in order to avoid further contamination of the Ash tree population. Now, the treated Ash trees, especially those along the entrance to the Leisure Center are showing leafed-out canopies and healthy looking green leaves. “We will continue to monitor the Ash trees throughout this summer. The fact that they survived last summer's drought, though, is a good sign,” said Krotz.
In 2014, the Des Plaines Park District will apply for a Reforestation Metropolitan Mayoral Caucus Grant to replace lost trees. The Grant allows for a 1:1 ratio of lost-to-replaced trees. “We will look for biodiversity in making our choices for new trees,” said Krotz, “and look to plant more native species as we did in the North Lake Park open space.”
For more information about the Des Plaines Park District, visit www.DPParks.org.