Emerald ash borer damage in Milwaukee County Parks

April 30, 2016

By Sheila Julson

Green Emerald Borer (insect) PHOTO Zerene Stacker/U.S. Geological Society

Green Emerald Borer (insect) PHOTO Zerene Stacker/U.S. Geological Society

Nearly 3,000 trees have been removed in Milwaukee County Parks since 2009 because they were infested with the invasive emerald ash borer. Others were cut down as a prophylactic to prevent further infestation, said Gregg Collins, forestry supervisor for the Milwaukee County Parks system. The emerald ash borer (EAB) is an invasive, wood-boring, metallic green beetle (Agrilus planipennis) originating in eastern Asia. It was first discovered in Wisconsin in August 2008.

The effect of the EAB is apparent in the defoliating Green Ash tree. PHOTO Wikimedia Commons/Bugwood Network

The effect of the EAB is apparent in the defoliating Green Ash tree. PHOTO Wikimedia Commons/Bugwood Network

“We are actively removing Green Ash trees (Fraxinus pennsylvanica), which are certainly infested and already debarked, and completely dead,” Collins said. “At the same time and often in the same park, we will remove Green Ash, which do not exhibit outwardly visible symptoms. We do this with the understanding that when EAB has infested an area, 100 percent of the remaining ash trees will become infested during the population explosion if not chemically treated with a pesticide.”

Lead Photo Culled Green Ash in HP

Two Green Ash trees were culled in Humboldt Park this spring. PHOTO Katherine Keller

Trees have been culled in many parks throughout the Milwaukee County Parks system, including Humboldt, South Shore, Bay View, and Sheridan on the South Shore. Collins noted that while they haven’t seen full infestation at Humboldt Park like in other parks, they did find EAB feeding galleries and the D-shaped exit holes in several trees near the tennis courts during the winter of 2014-15.

“We have confirmed EAB is present not only in our parks, but throughout the city of Milwaukee, other municipalities, and Milwaukee County in general,” said Guy Smith, chief of operations for the Milwaukee County Parks. “We have educated staff who know the signs, symptoms, and decline stages of trees that are victims of EAB infestation.”

An article published by the Wisconsin Department of Natural Resources states that “EAB larvae live underneath the bark of ash trees, feeding on the layer of the tree’s trunk that lies just below. When they do this, they cut off the flow of water and nutrients in the tree. Most trees die after about 3 years of infestation. The top of the tree begins to die first.”

When EAB symptoms are detected on ash trees in any region, they are subject to rapid decline. Because EAB larvae live and feed on the inside of ash tree bark, it is difficult to detect their presence until symptoms of damage occur.

Smith said Milwaukee County Parks prioritized park land into zones based on highest concentration of park patron use, focusing on playgrounds, picnic areas, and sections along roadways and bike trails. The practice of preemptive ash tree removal in high patron-use areas is a means to keep people safe from the falling limbs or trees weakened by the rapid desiccation caused by the EAB.

Green Ash trees. PHOTO Wikimedia Commons/Bugwood Network

Green Ash trees. PHOTO Wikimedia Commons/Bugwood Network

The staff of the Land Resources Division of Milwaukee County Parks also removes other tree species for specific safety or maintenance reasons. Some trees were removed recently along the west side of Lincoln Memorial Drive because they either possessed a defect that was going to lead to certain failure, were an undesirable species, or had a growing habit that was affecting vehicular, bicycle, or pedestrian use along the drive.

Green Ash tree leaves. PHOTO Wikimedia Commons/Bugwood Network

Green Ash tree leaves. PHOTO Wikimedia Commons/Bugwood Network

“The Land Resources Division of the Milwaukee County Parks Department puts a high value on trees and the benefit they are to each and every one of our parks and our environment overall,” Smith said.

During spring and fall, Milwaukee County Parks replants trees throughout the system, depending on available staffing and budgets. Smith said they try to replenish areas with trees where they would be most appreciated. “We plant a very diverse group of native tree species,” he said.

The mild 2015/2016 winter allowed the forestry staff to begin planting trees in February this year. The parks department partners with the Milwaukee Brewers and the Wisconsin Department of Natural Resources to plant donated trees, along with Keep Greater Milwaukee Beautiful, the Park People of Milwaukee County (Milwaukee County Parks’ overarching friends group), and park friends groups for reforestation efforts. Smith added that Friends of South Shore Park and Humboldt Park Friends have been valuable partners helping with planting trees, organizing clean up projects, and other projects in natural areas.

How You Can Help Prevent the Spread of Emerald Ash Borer

Do not transport firewood across county lines. EAB can hitchhike on firewood and invade trees in EAB-free counties. Buy firewood near your planned campsite and from state-approved vendors. For a list, consult http://goo.gl/Jla89f

Report ash trees showing signs on infestation to the Wisconsin Department of Agriculture, Trade and Consumer Protection. Email datcpemeraldashborer@wi.gov or call 800-462-2803. Learn the signs of Emerald Ash Borer infestation at youtube.com/watch?v=KJqnfWecZ9U

Sheila Julson is a freelance writer and regular contributor to the Bay View Compass.

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