Imidacloprid is a great tool for treating trees since it is effective for up to seven years following application and is relatively inexpensive. However, it is relatively slow-acting and can take up to a year to become fully effective in the canopy. While it is active in the tree, the tree’s HWA infestation will die, and HWA will be prevented from re-colonizing the treated tree, as individuals will die as they begin to feed.
Imidacloprid is a systemic insecticide, meaning that it works within the tree to fight off infestation. Imidacloprid is in a class of insecticides known as neonicotinoids. “Neonics” are often in the news since they are associated with increased risk to pollinating insects such as bees. Application for hemlock woolly adelgid, however, is a relatively safe context for Imidacloprid use since hemlock trees are wind-pollinated and bees do not rely on them as a food source.
The resources below are available for more information about Imidacloprid and the risks associated with its use.
Risk Assessment of Imidacloprid Use in Forest Settings on the Aquatic Macroinvertebrate Community
Elizabeth Benton, et. al. 2017
Optimized Dosage for Hemlock Woolly Adelgid Control in Hemlock Trees
Elizabeth P. Benton, Richard S. Cowles
“Hemlock Woolly Adelgid Management and the Ecosystem Risk of Insecticides”
Presentation by Dr. Elizabeth Benton, University of Georgia (as seen on Cornell University’s ForestConnect webinar series)
Join Dr. Elizabeth Benton, whose research on pesticide treatments for HWA has refined the management guidelines for treating large trees and assessed impacts to aquatic organisms. She will discuss recommendations for Imidacloprid applications, and share her research on the ecological risk associated with its use. Responsible Imidacloprid use results in minimal risks to forest streams, while preserving hemlock forests.
“Neonicotinoids, Bees, and Urban Trees: The Controversy Defined”
Dr. Richard Cowles, Connecticut Agricultural Experiment Station
Urban Forestry Today, hosted by Cooperative Extension of New Hampshire, produced this presentation on the hazards and appropriate uses of neonicitinoids in landscapes and natural areas.