You may have noticed some trees in Duluth neighborhoods are adorned with green ribbons. These ribbons are meant to raise awareness of the emerald ash borer (EAB) and the consequences of infestation among ash trees the City now faces. Please note, the ribbon does NOT indicate a particular tree has been infested, or is slated for removal or treatment. However, a majority of these ash trees are fated to die from this invasive pest.
EAB was detected in Duluth in late 2015, but recently-discovered infestations seem to indicate the borer has been here for a few years already. Unfortunately, widespread ash tree die-off typically occurs within a few years of a local EAB detection. EAB-infested ash trees become brittle and dry and decline very quickly. Ash trees that have died from EAB have a greater risk for sudden failure, potentially causing harm to people and property.
Among Duluth’s boulevard trees, ash is second only to maple in numbers. Approximately 2400 boulevard ash trees will quickly start becoming hazards as the local EAB infestation progresses. Because of this, the City plans to conduct a combination of preservation by chemical injection and pre-emptive removal of living ash trees on boulevards in order to prevent hazardous conditions. Generally, larger and higher-value ash trees will be targeted with injection by the City while declining trees and those under 12” DBH (diameter at breast height) will be removed.
In addition, through a partnership with the Minnesota Department of Agriculture, the City of Duluth is testing out the use of a biological control method with stingless wasps. The wasps work to consume EAB larvae and can help prevent the spread of EAB onto other ash trees. The test area is restricted to Hartley Park. The wasps pose no dangers to humans. Read more about biocontrol HERE.
In accordance with the City Council-approved Emerald Ash Borer Management Plan, the City will begin conducting these boulevard ash tree injections and removals in the Congdon, Morley Hts./Parkview, Hunters Park, and Woodland neighborhoods in 2017.
Most large, healthy boulevard ash trees will be preserved by the City by pesticide injection. Those under 12” in diameter will be removed while those near that measurement could be either removed or injected.