USA NPN National Phenology Network

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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. In southern states, the window for treating trees for this pest is now approaching.

Lilac Borer Current Day Forecast.

Lilac Borer 6-Day Forecast.

Pheno Forecast maps show when management actions should be taken for key pest species. These maps are updated daily and are available 6 days in the future.

Pheno Forecasts are based on published growing degree day (GDD) thresholds for points in pest life cycles when management actions are most effective. Forecasts are currently available for five insect pest species.

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 on the sidebar on the right side of this page. 

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.

Treatment Summary

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

The forecast above is a real-time, high-resolution forecast which estimates the appropriate time to spray pesticides to prevent infestation by lilac borer. 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. Adult emergence begins around 500 Accumulated Growing Degree Days (AGDD) and continues until approximately 1,400 AGDDs; sprays should be implemented for this entire duration. The Pheno Forecast map indicates when sprays should occur to control lilac borer. AGDDs are accumulated from a base temperature of 50oF.

Source: Potter and Timmins (1983)

More information on map development and re-use policy.

Treatment guidance

UMass Amherst Center for Agriculture, Food, and the Environment

Colorado State University Extension


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