Hemlock Woolly Adelgid Forecast

Hemlock woolly adelgid can be deadly to hemlock trees and, in the eastern United States, lacks enemies that keep their populations in check. Researchers wish to identify the optimal window to release insect predators; you can support this effort by observing hemlock woolly adelgid life cycle stages using Nature’s Notebook

Hemlock Woolly Adelgid Current Day Forecast

Hemlock Woolly Adelgid Six-Day Forecast

WHAT ARE PHENO FORECASTS?

Pheno Forecast maps predict key life cycle stages in invasive and pest species, to improve management efficacy.  For insect pest species, Pheno Forecasts are based on published growing degree day (GDD) thresholds for key points in species life cycles. These key points typically represent life cycle stages when management actions are most effective. These maps are updated daily and available 6 days in the future.

Help us improve these maps! Our Pheno Forecast map products are still in development, and we seek input on their performance in your area. Give your feedback at the bottom of the page.


Credits: Elizabeth Willhite, USDA Forest Service via Bugwood.org
Image
Hemlock wooly adelgids on a hemlock branch (appear as white fuzz on the branches)

SPECIES BACKGROUND

Hemlock woolly adelgid (Adelges tsugae) damages hemlock trees by piercing the twig at the base of the needles and sucking sap from the trees. Native to East Asia, it now occurs in forests in the eastern US as well as in the Pacific Northwest. In the Northwest, it is kept in check by natural predators; in the east, where predators are few, this pest is causing major damage to hemlock forests. Researchers are working to identify the best time of year to release predator insects or biocontrols, that would limit the rapid spread and damage of the hemlock woolly adelgid. 


Credits: Nick Dietshler
Image
Close up of hemlock branch shows small brownish eggs of the hemlock wooly adelgid.

EGG AND NYMPH FORECAST

We forecast the timeframe to look for eggs and nymphs based on growing degree days.  For specific information on preferred treatment options in your region, we recommend contacting your local extension agent.


EXPLORE THIS FORECAST

Learn more about this forecast using our visualization tool!

Phenophase

GDD threshold

Base temp

Start date

GDD method

Model origin

Source

Eggs

26-1000oF

32oF

Jan 1

Simple average

NY

Cornell University

Nymphs 1001-2200oF 32oF Jan 1 Simple average NY Cornell University

More information on map development and re-use policy.

TRACK THIS SPECIES WITH NATURE'S NOTEBOOK

 

You can help verify this forecast by checking trees for this species and reporting your findings in Nature’s Notebook via the Pest Patrol campaign. Your observations will help scientists better understand when this species is active and susceptible to treatment.

 

Learn more about Pest Patrol

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Give us your feedback on our Pheno Forecast maps

Have you used our Pheno Forecast maps to plan treatment activities, or to know when to search for pests of interest? Do you have a suggestion of another species for which a forecast would help you make decisions? We'd love to hear about it!

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