Elkhart Historical Society lecture series features Guy Sternberg and the War on Emerald Ash Borer

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[May 23, 2023]   On Friday, May 19th, the Elkhart Historical Society held a dinner lecture at the Wild Hare Café. The featured speaker was Guy Sternberg who discussed the emerald ash borer war and the blue ash trees on Elkhart Hill.

Gillette Ransom of the Elkhart Historical Society introduced Sternberg.

Sternberg owns the Starhill Forest Arboretum and has written three tree books with his most recent being Native Trees of North America from the Rockies to the Atlantic.

As Sternberg began his lecture, he said that trees affected by emerald ash borers (EAB) generally die. There are few natural predators of ash borers currently present in North America. When it comes to emerald ash borers, black ash and green ash trees are especially affected because the borers love them and white ash is not far behind.

The blue ash tree is not closely related to green and black ash because blue ash has a different metabolic and structural system. Sternberg says that is a point in its favor. Blue ash is the main species on Elkhart Hill and there are several very old blue ash trees at the Elkhart nature preserve which have not been affected by ash borers.

Sternberg showed photos of various ash trees. The markings show the EAB infestation. If the problem is caught early, these trees can be saved. Looking at the condition and size of the growth from year to year is important. If the growth has slowed, Sternberg said you better do something soon if you desire to save the tree.

Early on, Barney traps (so-called because of their purple color) on trees were used to track the spread of the invading insect. The traps were something that Sternberg says won’t kill any significant number of ash borers but can confirm their presence.

When looking at ash trees, Sternberg said shorter annual twig growth, branch die-back and “D” shaped holes indicate problems. This creates a bleaching, a pale colored appearance of the bark in these areas. Woodpeckers can hear EAB munching on the trees and will remove outer bark in an attempt to get at the larvae. Sternberg said that alone does not solve the problem but gives us one piece of the puzzle.

Where ash tree bark has already sloughed off, back and forth squiggles tracks on the trunk show where emerald ash borers have taken out the tissue of the tree. Sternberg said the tree is basically dead by that point.

Questions Sternberg said you should ask are do you want to save the tree? Is it worth saving? How large is it? Will you commit to treating the tree for the foreseeable future either annually or periodically?

If you decide to treat the tree Sternberg said is important to know that the cost of treatment versus removal of the tree is about equal.

Along with many others, Sternberg has been working to save ash trees. Some years ago, while he was driving through Kentucky, Sternberg found an old highway right-of-way full of dead white ash trees. But there was one survivor tree, which can be useful for resistance breeding. A nearby rest area had many trees that were being treated and all had survived.

Information from Michigan, Ohio and Kentucky, where blue ash is much more common than it is here in Illinois, suggests that some of these trees might be able to survive the emerald ash borer.

What Sternberg has found is that in the bluegrass country of Kentucky, where limestone soils are well suited to blue ash, observations have found that roughly 40 percent of the trees that had been healthy when the borer arrived were still alive as the pest population began to crash after about 10 to 12 years due to loss of their food source.

The goal for Elkhart Hill was to bring as many of the ancient trees there as possible into that 40% category with a one-time treatment funded by private donations. In a three-week media blitz, Sternberg said “we found so many generous people who agreed with that goal that we were able to raise $14,000.” They realized no one in the country had tried to do a media blitz like this one to help with the problem.

Here is the story:

In April of 2021 on Elkhart Hill someone inspected the nature preserve with Sternberg and they found a couple of dead ash trees along the exposed edge of the area. They were not leafing out, but many others were. The goal established for Elkhart hill was to reinforce as many ancient trees as possible to preserve them until biological controls could take over.

May 23, 2021, Sternberg and others began doing an Elkhart tree inventory. He said they could do a certain number of inches in diameter based upon the amount of money they had raised and were looking at how many trees there were and how big they were. The group wanted to save some of the best trees, the medium sized trees still in good shape, and ones that had room to grow. They also wanted to have some un-treated control trees to see if they also would survive. After an initial walk through, the group started measuring and marking trees, compared notes, and added GPS locations and photos to find them later.

Sternberg said they had to get permissions and regulations from Elkhart Hill Grove Nature Preserve (a private owner) and the Illinois Nature Preserve Commission to comply with nature preservation policies.

To treat trees Sternberg said they used Emamectin Benzoate, which cost more than $500 a bottle. On June 16 and 17, 2021, treatment began with injecting thirty-two big blue ash trees. They also arranged for eager adjacent landowners to have their own trees treated.

On May 21, 2022, there was an Elkhart hill lightning strike at the end of a stormy research tour. Sternberg said it was less than 100 feet from where he was standing, shook the ground, and created a deafening sound and blinding light. At that point they left the grove of trees for safety reasons. In October 2022 Sternberg and others went back and found the two ash trees that had been struck by lightning. They were blown apart, but one was still sprouting.

In fall of 2021, Sternberg and others began to gather seed to grow seedlings and establish a new cohort (a successive generation) of trees at the Elkhart nature preserve. Sternberg said the team gathered local provenance seeds from female trees in Elkhart. Some of the blue ash trees on Elkhart Hill are old enough to predate the Revolutionary War.

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Next, they had them propagated (which is not easy) at a commercial plant nursery in Missouri and grew them into small seedlings for planting in the nature preserve in spring of 2023. Donations were collected to raise money for the new trees and several volunteers helped with the planting.

All of it was done with permission and assistance from landowners and participation by the Illinois Nature Preserves Commission.

Sternberg said they started with only thirty-two small trees grown from local provenance, but if those trees mature, they will create a new generation of this rare forest species.

When working on a nature preserve Sternberg said you do not want to mix with the genetics of the preserve because it contaminates what is already there.

When planting the trees in the preserve, they created open sky for the seedlings by removing some existing groups of surplus sugar maples. Deer resistant barriers were built using twigs and branches from the downed maples on site, so no foreign wood or metal was introduced to the preserve and no plantings from other areas were brought in.

Elkhart Hill was also found to have had the largest Blue Ash (fraxinus quadrangulata) in Illinois, making it the new state champion for this species on the Illinois Big Tree Register.

To do tree breeding for future resistance Sternberg says you should harvest seeds and scions from survivor trees of any affected ash species for future resistance breeding.

The National Ash Tree Seed Collection Initiative is one organization trying to collect trees for preservation. A brochure they have put out says: “America is losing its ash trees at an alarming rate. An invasive species, the emerald ash borer, has already destroyed millions of ash trees.”

Because of that, “the loss of all of America’s ash trees is a real possibility. An effort is underway to gather seed from populations of native ash tree species nationwide.”

The initiative is asking people to assist in the effort by collecting ash tree seeds and sending them to the Rose Lake Plant Materials Center in East Lansing, Michigan.

When collecting seeds, the National Ash Tree Seed Collection Initiative says to collect at least 500 seeds from each population and check that seeds are filled. When mature the “seed is typically brown to tan in color and separates easily from the tree.”

Once you have collected seeds, they should be put in a cloth or paper bag and stored in cool, dry conditions until you are ready to ship them. Do not put them in a plastic bag.

Though emerald ash borers continue to be a problem Sternberg says they're hoping to have biological controls. The USDA says, “there are four known stingless wasps from the emerald ash borer’s native countries that will attack either EAB larva or eggs.” The USDA Agricultural Research Center is currently evaluating a fifth wasp.”

In an article on Biological Control, it says, “for several years now, APHIS has been turning EAB’s natural enemies—these tiny stingless wasps—into biological control agents. The wasps are already showing promise in a number of states, especially in terms of protecting young saplings from EAB.”

At this point, at least one of the four stingless wasps has been released in 25 (infested) states. The offspring of these wasps have been recovered in 17 states. The USDA says it shows “the wasps are establishing, reproducing, and, more importantly, attacking and killing EAB.” Additional good news for central Illinois is that a wasp release has just been approved for public land in the Lincoln area this year!

The plan is “significantly expand the distribution and increase the number of wasps released in infested states to help stabilize and eventually reduce EAB populations.”

As Sternberg says, we need to find ways to preserve what we do have. In finishing his talk, Sternberg expressed thanks to all the people made it possible.

One question was about treatments such as drenching a tree’s base and why it is not effective on large trees.

The problem is uptake and longevity. Sternberg said if you are mixing up a soil drench to pour around the base of a tree to let roots absorb, you are counting on the roots absorbing enough to go up through the entire tree and out to the leaves. You are counting on that happening at a time when the beetles are starting to reproduce.

When using the basal drench system Sternberg said that must be done every year and he would only recommend it for small trees. Larger trees cannot absorb enough of the insecticide to reach all of the way up the tree. In the next year, the treatment would have to be done again.

Sternberg said mechanized infusion treatments with Emamectin chemicals kill what larvae is in the entire tree. The process is expensive and invasive but it can last for up to three years because the chemical goes straight through the tree and acts both as an insecticide and a deterent.

With the parasitic wasps someone asked how hopeful he was that they would begin to make a dent in the problem. She wanted to know the long range prognosis for using these wasps.

For a while, Sternberg said we will need to keep treating other ash trees to get them past the surge of the emerald ash borer. Sternberg said people need to continue to protect trees. As wasps kill borers and the wasps reproduce, it will create a balance so there are not as many borers around that will overwhelm a tree. Hopefully woodpeckers will continue to adapt to feeding on the larvae and other controls will increase as well.

When it comes to the National Seed Collection initiative someone asked whether it applies to just to blue ash or all ash trees. Sternberg said the collection initiative applies to all native ash species.

Sternberg was also asked when the ash tree seeds mature. He replied the seeds mature in early fall.

A final question was about the growth rates of ash trees.

Sternberg said that if healthy they can grow a foot or more each year.

The next Elkhart Historical Society dinner lecture will be held Friday, June 23 at 5:00 p.m. at the Wildhare Café in Elkhart. Reservations can be picked up at the café and must be turned in by June 16.

The speaker will be Professor Tony Rothering of Lincoln Land Community College. Rothering is an official bird bander. Recently, he was in Elkhart and was able to catch and release 120 different birds after banding, measuring and recording them. Rothering will explain what is going on with our climate and what it is doing to migration patterns we have been able to observe through the years. Ransom said Elkhart is an oasis for migrating birds.

[Angela Reiners]

Related information:

Guy Sternberg

Rose Lake Plant Materials Center
USDA-NRCS 7472 Stoll Road
East Lansing, Michigan. 48823
Telephone: 517-641-6330

Email: john.lief@mi.usda.gov
(If possible, email Lief after sending seeds)


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