Breeding Emerald Ash Borer Resistant Ash

​By Chad Gadsby, Service Forester
By now most of you are aware that ash throughout the region are mostly dead or dying due to emerald ash borer (EAB) infestation. The US Forest Service has been working since 2018 to develop a process and begin breeding EAB resistant ash out of their Delaware, Ohio research lab. The goal is to breed a genetically diverse population of all ash species native to the US.
To accomplish this task, they developed a set of criteria to identify healthy and/or lingering ash that carry some form of resistance.

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​Criteria

• ≥95% mortality of mature ash trees has occurred at least 2 years ago (~4 years after 50% mortality was reached)
• Tree was large enough to have been infested during the peak EAB infestation (>4” DBH)
• Tree currently has a healthy canopy
• Natural trees only! (Planted cultivars have already been tested since they are clones)
• No insecticide treatment history!

Potentially resistant trees are being sought from across their range because it is critical to capture the widest array of genetics possible. The genes that are responsible for EAB resistance are considered rare in the ash populations because there was no selective advantage prior the introduction of EAB. Due to the rarity of these resistance genes on the landscape, the widely spaced trees are not likely to be able to cross pollinate and reproduce on their own. This is where the breeding program comes in.
Breeding
After selecting a potentially resistant ash, branch or twig samples are taken during the dormant season. From these samples, scion wood is grafted to rootstock. Hot-Callus Top Grafting is the preferred method for this initial graft as larger wood can be used. Once the graft takes, the tree is challenged with EAB eggs. The tree is then monitored to see how the EAB larvae develops. If the tree displays resistant traits, scions are collected, and bud grafted to rootstock to be used in the breeding program. Using these techniques, Forest Service researchers have found that some offspring from these originally grafted trees have accumulated more resistance than their parents individually.
You can help this breeding program by searching for and reporting lingering and/or healthy ash by following the instructions on the Ecological Research Institute’s (ERI) Monitoring and Managing Ash website (www.MonitoringAsh.org).
Information for the article was compiled from US Forest Service’s Urban Forest Connections webinar on March 11, 2020 titled “A Call to Action For Ash Tree Conservation And Resistance Breeding.” 
 
An Addition to Chad’s article- Need trees?
The Bradford County Conservation District has an annual tree sale.  This sale is typically in the spring of the year.  This year, for several reasons, we have went with a fall sale.  Trees will still be delivered in the spring, but having the order ready, and securing the trees this early will really help us get what we want.  We have picked out some more unique trees this year for the sale.  We also have some shrubs, food plot mix, and birdhouses.   The deadline is November 30th, so time is of the essence.  Please call the District or visit our website to order.
 
The Bradford County Conservation District is committed to helping people manage resources wisely.  You can visit the Bradford County Conservation District at 200 Lake Rd in Wysox across from the Wysox Fire Hall. Contact us at (570) 485-3144 or visit our web page at www.bccdpa.com.