Title
ADDRESSING APHID INFESTATION COMPLAINTS WITHIN THE URBAN FOREST
COUNCIL STRATEGIC INITIATIVES ADDRESSED:
Preserve and enhance neighborhoods
Address quality of place issues
Provide sustainable water quality and environmental infrastructure
CITY ATTORNEY: N/A
SUMMARY STATEMENT:
In 2012, City Council approved the Tree Board’s (a.k.a. the Parks and Recreation Advisory Board’s) recommendation to suspend chemical applications to control aphids in city birch trees and to pursue a birch tree removal and replacement plan. At the time of this recommendation there were 924 birch trees within the city limits and it would take 10 years or more if the city were to eliminate the birch monoculture that exists along city streets. The recommendation from the department was to reduce the number of birch trees to reach a “tolerable” level of infestation complaints rather than removing all of the trees without an evaluation period. The recommendation included focusing on areas that historically have had the greatest numbers of aphid complaints.
In 2013, City Council approved Ordinance Number 3248 amending the Urban Forest Maintenance Management Plan. After two years of local testing of the chemical application, the City Council concurred with the recommendation from the Tree Board to suspend the use of Imidacloprid (Merit®) as a means of aphid control in birch trees because of its questionable effectiveness. The ordinance amended the chemical application policies contained within the plan and adopted minor revisions to the city tree removal criteria.
In 2013 and 2014, the department embarked on the birch tree removal program, removing approximately 100 birch trees in both years and reducing the number of birch trees from 924 to 701. After the first year of removals there was a reduced number of complaints regarding aphids.
2015 was determined to be an evaluation year to assess the impact of the removal program. There was a marked reduction in the number of calls received regarding aphids that year, but in 2016 there was an uptick in complaints. The calls taken in 2016 reported a wider variety of species that were being impacted, such as basswood and linden. Aphids are species specific, so a birch aphid would not be found on a basswood. Urban forestry research provides data which show the removal of a birch tree would not have an effect on the aphid infestation on a different species of tree. Additionally, once a specific aphid variety living in a certain species of tree is removed, they do not migrate to another type of tree nearby. In addition to being species specific, aphid infestations are affected by weather and precipitation, so they can fluctuate from year to year.
Department staff presented to the Tree Board the option of once again introducing the use of Imidacloprid (Merit®) but on a far smaller scale. We would like to address each individual citizen’s complaint with the use of the insecticide and take responsibility for the application, watering, and monitoring of the chemical.
Historically, the Parks Division scheduled the application process to broadly treat all of the birch trees with the hope that wet weather or homeowners would help water in the granular material. This broad spectrum approach was costly in product and labor time and not always as effective as the product has proven to be because of variables in application. The hope is now that our management of the application will accomplish two goals, the first goal being the successful application in a timely manner to ensure proper coverage and application of the product. The second goal is to provide quality customer service to our citizens in addressing their complaints with action.
The Tree Board has recommended that Council reinstate Imidacloprid (Merit®) insecticide use on a case by case basis with an evaluation of the implementation and success at the end of the year.
MOTION:
Motion to direct the City Attorney to prepare an ordinance to allow the use of Imidacloprid (Merit®) insecticide use for the treatment of aphids.
STAFF CONTACT:
Jennifer Wills, Director Parks and Recreation
Curt Nedved, Urban Forest Manager