Planning to protect Ash Trees from EAB – Timing is important
By Sam Custer
OSU Extension, Darke County 

The EMERALD ASH BORER (EAB) has killed millions and millions of ash trees in urban, rural, and forested settings.  The beetle was first discovered in 2002 in SE Michigan, and Windsor, Ontario.  Almost 13 years later, EAB has been found in 19 states.  Over the years, scientists have learned much about this non-native insect and methods to protect ash trees. 

There are several options available and research has shown that treatments can be effective.  To answer questions that homeowners, communities, and tree care professionals have, researchers from Ohio State University, Michigan State University, Purdue University, University of Wisconsin, and University of Illinois co-authored a bulletin, Insecticide Options for Protecting Ash Trees from Emerald Ash Borer.  Additional treatment related resources include:  Emerald Ash Borer Management Statement; and Potential Side Effects of EAB Insecticide FAQs.  These resources are available on the OSU AshAlert website at http://ashalert.osu.edu or on the regional EAB website at http://emeraldashborer.info.  

While there isn't a single treatment plan or one application method that works best under all circumstances, the timing of the treatments can make or break effectiveness and ultimately the results.  Studies have also shown that it is best to begin using insecticides while ash trees are still relatively healthy.  Trees exhibiting more that 50% die-back, are probably too far gone and treatments are usually not recommended.   

Researchers have learned that if the canopy of an ash tree is already declining when insecticide treatments are initiated, the condition of the tree may continue to deteriorate during the first year of treatment.  In many cases, scientists observed that the canopy will begin to improve the second year of treatment.  This lag in the reversal of canopy decline probably reflects the time needed for the tree to repair its vascular system after the EAB infestation has been reduced.  

Methods of applications include soil injection, soil drench, trunk injection, systemic bark sprays, and preventive bark and foliage cover sprays.  Recommended timing for soil injections and soil drenches is mid to late spring.  Trunk injections are typically made beginning in May - mid June, as it doesn't take as long for the product to be moved through the tree.  Preventative bark and foliage cover sprays are usually made in 2 applications at 4 week intervals.  The first of the treatments should occur when black locust is blooming.  This is typically in early May in southern Ohio, and late May in northern Ohio.   

Homeowners may want to treat their trees themselves using an over-the-counter soil drench product.  Trees greater in size than 15" diameter at breast height (DBH) should be treated by a licensed pesticide applicator. 

Last month, Dr. Dan Herms presented a web-based session as part of Emerald Ash Borer University (EABU) - A Research Update on Insecticide Options.  This session, and other hour long EAB related sessions can be viewed from the Regional EAB website at http://emeraldashborer.info.   

For more detailed information, visit the Darke County OSU Extension web site at www.darke.osu.edu, the OSU Extension Darke County Facebook page or contact Sam Custer, at 937.548.5215.