Keeping the Legacy Alive

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Chemical pesticides are widely used as a primary defense against hemlock woolly adelgid (HWA) populations in the US. Chemical control can delay adelgid impacts, essentially providing a ‘life support’ for the trees and allowing more time for nature to adapt and for the development of longer-term solutions. In the US, it has been the most successful short-term method available for protecting high-value hemlock trees and slowing the spread of HWA. Chemical treatments to save trees may take as long as two years to translocate to the tree canopy where it becomes effective against HWA. A hemlock tree may lose capacity to translocate the chemical, and recovery will not be possible if treatment is not delivered early enough.  

Insecticides to control HWA

To find out more about potential impacts of chemical treatments go to our resource page.

Certified Pesticide Applicators (HWA)

To inquire about chemical treatment for hemlock on your property please contact a licensed applicator. Contact list will be updated as more licensed applicators become available.


Scott Robinson 
Cell: 902-875-7686 

Less toxic control products

Insecticidal soaps and horticultural oils have been used instead of insecticides. They have a low toxicity and have been effective when properly applied. Multiple applications are required and thorough coverage on larger trees is extremely difficult. Horticultural oils function by suffocating the adelgid; infested needles and well-protected waxy ovisacs must be completely drenched. Traditional pyrethroids (an organic compound found in the majority of household insecticides) and other pesticides are considered less effective than systemic insecticides because of the difficulty in achieving adequate coverage and the larger amounts required for external spray applications, greatly increasing the toxicity exposure to other organisms. Other less toxic insecticides are also being tested by the Canadian Forest Service. Please carefully consider the options available and consult with a professional certified pesticide operator if you decide to use neonicotinoids to help keep hemlock alive and mitigate the spread of HWA on your property.