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Hemlock Woolly Adelgid Pheno Forecast, Contiguous United States, 2016 - Current Year

posted on 2021-04-22, 20:46 authored by USA National Phenology Network
Pheno Forecast maps predict key life cycle stages in a range of species to improve conservation and management outcomes. 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. We forecast eggs in hemlock woolly adelgid (Adelges tsugae) at 26-1000F growing degree days (base 32F, start date: January 1, simple average GDD method). We forecast nymphs in hemlock woolly adelgid at 1001-2200F growing degree days (base 32F, start date: January 1, simple average GDD method). Forecasts are available for the current and prior year in the the USA-NPN Visualization Tool ( and 2016-present through USA-NPN Geo Web Services (available upon request). Hemlock woolly adelgid damages hemlock trees by piercing the twig at the base of the needles and sucking sap from the trees. These forecasts are designed to guide researchers and volunteers by providing the timeframe during which to look for each life stage.

For all inquiries regarding this dataset, please contact the USA-NPN. This data is subject to the USA-NPN's Data Use Policy.


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