Chemical Treatment for Landowners

Step 1: Do you have hemlocks?

If YES, go to Step 2.

If NOT SURE, click the link to get help identifying your tree: Is it a hemlock? (¿Es un hemlock?)

Step 2: Is your hemlock infested by hemlock woolly adelgid (HWA)?

If YES, go to Step 3.

If NOT SURE, click the following link to get help identifying HWA and other common hemlock pests: HWA Identification Guide

If NO, do not treat for HWA. Why?

If your tree’s health is declining due to something other than HWA, then chemically treating they way you would for HWA may not help that problem and could make the real problem worse.  See the HWA Identification Guide for other possible pests and diseases that may be affecting your hemlock.  If you are unable to see HWA on your hemlock during the winter or you are unable to reach a living branch, you may need to consult a professional.  If you do not see HWA and your tree looks healthy then you can either treat prophylactically as a defense against HWA, as imidacloprid can last for multiple years, or you can monitor for the appearance of HWA and any decline in tree health.

Step 3: Assessing the severity of the situation

The following documents will help you determine whether your trees will respond to treatment:

• • • • Hemlock Health Assessment Guide

You can also send us photos to help us better inform you. Here is a document on how to take useful photos: Photographing a Tree

Step 4: Location

The setting in which your trees are located may influence your treatment options. Please select from the following list to learn about location-specific considerations:

• • • • Open, landscaped or yard-like environment
      • Forested, closed canopy
      • Steep slopes
      • Wet, seepy areas with saturated soils
      • Sandy soils
      • In immediate proximity to flowering plants

Step 5: Hemlock woolly adelgid treatment options

Click on the following links to learn about chemical treatment options

• • • • Instructional video: “How to Treat Hemlocks for HWA”
      • General HWA Treatment Info
      • Simple Soil Drench Instructions (and CoreTect tablets)
      • Imidacloprid vs. Dinotefuran Comparison
      • Chemical Product Comparison Chart
      • List of professional hemlock treatment providers

After you have treated your hemlocks, please fill out our Hemlock Treatment Follow-up Survey.

Environmental Risks

Any management decision for your hemlocks (including taking no action) involves trade-offs. Learn more about the risks of off-target impacts from chemical treatment with imidacloprid in this publication by researcher Elizabeth McCarty from the University of Georgia. (Citation: McCarty, E. 2020. Environmental Risks to Arthropods from Imidacloprid Applications for Hemlock Conservation University of Georgia Warnell School Outreach Publication WSFNR-20-88A.)

Still have questions?

Call us at 828-252-4783 or email info@savehemlocksnc.org with your questions, and we’ll do our best to point you in the right direction.