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Monday, Sep. 8th 2014

Should I Treat My Ash Trees for the Emerald Ash Borer?

If you live in a county where the emerald ash borer (EAB) has been detected, insecticide treatments are a viable option to protect ash trees. But fall is not the best time. Insecticide treatments are most effective against EAB when applied in the spring.

But first, a homeowner should answer a couple questions.

  • Which ash trees are worth saving? Trees in poor health (more than half their leaves missing) or growing in a poor location (e.g., near utility lines) are not worth treating.
  • Is EAB nearby? Insecticide treatments are not recommended if EAB is not in your county or within 15 miles. Consult the map of EAB positive counties.

Trees with a trunk diameter smaller than 15 inches can be treated by the homeowner with a soil drench preparation of Imidacloprid. Larger trees should be treated by a certified arborist. Homeowner applications of Imidacloprid can be made in early spring until the time of pear or crabapple bloom, or typically from March to mid-April. Applications must follow label directions. Tree care professionals have additional options for types and timing of insecticide applications. Click here for more information.

A revised edition of “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer” is now available. This comprehensive guide provides the latest information on effective use of insecticides against EAB.

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University of Missouri Extension Master Gardener Program