USA NPN National Phenology Network

Taking the Pulse of Our Planet

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Lilac borer adult

Lilac borer is a common wood borer that damages lilac (Syringa spp.), ash (Fraxinus spp.), and privet (Ligustrum spp.) shrubs and trees.

Image credit:
James Solomon, USDA Forest Service,

Lilac Borer Forecast

Lilac borer is a clear-wing moth that can damage lilac, ash, and privet trees and shrubs by burrowing into the heartwood. 

Lilac borer current day forecast

Lilac Borer Current Day Forecast.

Lilac borer six day forecast

Lilac Borer 6-Day Forecast.

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.

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Species Background

Lilac borer (Podosesia syringae), also known as ash borer, is a clear-wing moth that is native to North America and widespread in the U.S. The larvae tunnel into the trunks and lower branches of lilac, ash, and privet. Trees stressed by drought, injury, or recent transplanting are especially susceptible to borers.

Adult Forecast

Larval Lilac Borer, Photo: David Cappaert, Michigan State University

We forecast adult emergence based on growing degree days. Adult lilac borers overwinter in the heartwood of trees, then emerge in early summer. Trunk sprays should take place preceding or coinciding with adult emergence and subsequent egg hatch to kill larvae before they enter trunks. For specific information on preferred treatment options in your region, we recommend contacting your local extension agent.   For more information, visit UMass Amherst Center for Agriculture, Food, and the Environment or Colorado State University Extension


GDD threshold

Base temp

Start date

GDD method

Model origin


Adult emergence



January 1

Double sinte


Herms (2004)

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