Emerald Ash Borer in Princeton

Here's a stock photo of the recently arrived insect that will kill (there must be a better word) Princeton's most numerous tree species over the next decade. White ash, green ash, and the much less common black ash--all are vulnerable. The photo shows an ash tree with characteristic "D"-shaped exit holes. It will take a lot more than a penny to deal with the consequences of this diminutive beetle's appetite. I'll expand below, but I sent the quick read version out in a mass email that was then quoted in an informative article in the Town Topics:

"Emerald Ash Borer (EAB) was found in a trap set by the town arborist out along River Road. This small green insect, accidentally introduced to our continent from Asia, probably in wooden packing crates, has been spreading outward from its original introduction in the Detroit area, killing 100s of millions of ash trees. The insect will spread across Princeton over the next few years, eventually affecting all ash trees that haven't been treated. Highly valued ashes can be injected in springtime with an insecticide. The treatment can provide protection for several years. Of the various chemicals available, I've heard the most praise go to Arbor Mectin. Tree-Age has a similar formulation."

The Next Fifteen Years

So, what happens now, and what can we do about it? Princeton's arborist, Lorraine Konopka, sees this slowly evolving catastrophe following a fifteen year arc. In the first five years, EAB will spread around town, building up its numbers with each new generation. Symptoms are slow to manifest, but in various ash trees we'll start seeing dieback starting at the top of the crown and working its way down. Many ash trees are already suffering from ash decline, notably a disease called ash yellows, making it even harder to know for certain when EAB has invaded a particular tree. Homeowners will be forced to choose between spending hundreds of dollars every few years to treat favorite ash trees with systemic insecticide, or spending thousands of dollars later on to remove their dying ash trees before they become brittle and dangerous. The five years that follow will be marked by radical dieoff, both in town and in our nature preserves. Some woodlands where ash trees dominate will be decimated. We'll see otherwise green hillsides dotted with skeletonized remains of ashes. The five years after that, more or less, will see the last untreated ash trees succumb. The population of EAB will drop dramatically, but protected trees will continue needing new injections of insecticide, though potentially less frequently. Ash trees will still be found in nature preserves, but likely get attacked as they grow towards maturity. More on the aftermath at this post, written after a visit to Ann Arbor, MI.

Life Cycle

According to an EmeraldAshBorer.info webpage, the Emerald Ash Borer hatches into an adult in May and June (coincidentally, emergence is said to begin around the time that black locusts bloom), flies to new areas and mates in June and July, then lays its eggs in August. The larvae feed just inside the bark in the fall, then overwinter as pre-pupae before hatching into a new generation of adults the next spring.

So it's not surprising that the first confirmed sighting of an emerald ash borer in Princeton happened in late July, when one was found in a trap placed near River Road by the town arborist. Previous documentations in the area were in Bridgewater, West Windsor and other towns.

Treatment to Protect Ash Trees

Homeowners will need to decide, over the next year or two, which if any ash trees they wish to treat. The expense of recurrent treatments, and the ongoing benefits of the tree, need to be weighed against the cost of removal. This definitive article recommends treatment of trees if EAB has been found within 10-15 miles, which is now the case for Princeton. Treatment is most effective in the spring, between mid-May and mid-June, just after the tree leafs out. The article confirms the superior performance of emamectin benzoate, the active ingredient in Arbor Mectin and TreeAge. This insecticide may be more expensive than others like imidichloprid, but lasts longer and has a higher success rate. For more on my research on this issue, scroll down at this link to "How to save specimen ash trees".

Natural Predators of EAB

Woodpeckers are said to eat 80% of the EAB, but that's not enough to stop it. There are native parasitic wasps that also prey on EAB, but not in sufficient numbers. Some parasitic wasps species from the EAB's native range in Asia are being introduced (hopefully with a great deal of prior testing to show they won't prey on our native insect species), but I doubt they will influence the arc of Princeton's infestation over the next decade.

An article in the NY Times discusses techniques to stimulate the defense systems of ash trees so that the tree itself will manufacture sufficient chemical defenses to ward off EAB, but again, any practical use is highly speculative.

What's a Dead Ash Good For?

Strangely, there seems to have been no planning at any governmental level to at least put the coming surge in dead wood to use. Talk of sustainability and the opposition to fracking and natural gas pipelines are weakened if we ignore local sources of renewable energy. Lacking wind, we need to turn to sunlight. Solar panels, now essentially free to install, are an obvious option, but for some reason wood is being ignored. Europe has clean incinerators that generate energy from wood chips. Ann Arbor trucked its ash trees to an energy-generating facility in Flint. Unlike the carbon from fossil fuels, carbon from trees comes from the atmosphere, not from underground, so there is no net increase in above-ground carbon when wood is burned. Composting requires considerable fossil fuel for turning and transporting the compost, and decomposition releases as much carbon as burning.

In addition, the EAB invasion is coming just as Princeton's collection of loose yardwaste is being expanded. There is no effective incentive yet in place for homeowners to trim their dependence on this costly program, and the addition of 1000s of ash trees to this already over-burdened collection service could overwhelm the capacities of the public works department and local composting sites.

Possibly relevant, the state compiled this list of "Forest Industry Professionals Accepting Ash Trees".

Previous Posts

The Emerald Ash Borer's arrival in Princeton had been long anticipated. Some fifteen posts on this blog mention it, dating back to April, 2010, when I wrote,

"In Princeton, we will over the next decade likely witness a dieoff approaching the scale of the chestnut and elm dieoffs of the 20th century, as the emerald ash borer, which hitch-hiked to Michigan from Asia in wooden packing crates, continues its spread eastward. There will, in other words, be a lot of gaps in the canopy for the chestnut to claim, if its return is successful." 

That last part, about a resurgent American chestnut filling the gaps as we lose our ashes to the Emerald Ash Borer (EAB), as the previous post about chestnuts shows, was a nice concept but overly optimistic. Here's a particularly extensive post on EAB, in which I included notes from a phone call with the division chief of Forest Pest Management in Pennsylvania, where they've been dealing with EAB for years.

After Emerald Ash Borer, What Will Princeton Look Like?

Back in July, I took a trip to the future. Princeton still has a few years before the emerald ash borer is expected to decimate our ash trees (what a cheery sentence that is), but Ann Arbor, MI, has already weathered the EAB storm. The city is located less than an hour away from the original introduction of the insect, which went unnoticed in the Detroit area from the early 90s through to 2002 when it was finally identified. The introduction was likely via wooden shipping crates arriving in Detroit/Windsor from China.

Ann Arbor's tree removal lasted ten years and cost $5.8 million. What does this city of 110,000 look like now?

By chance, my trip to Ann Arbor coincided with a visit by college friend and early EAB researcher Dave Cappaert. We visited County Farm Park, one of the sites where he and fellow entomologists did the dirty work of cutting open some 10,000 ash trees to study the behavior of the emerald ash borer and search for parasites that might help control its numbers.

While immersed in research on EAB, Dave discovered a formerly unknown braconid wasp that parasitizes EAB larvae, and now bears his name: Atanycolus cappaerti. Other useful parasites have also been discovered, here and in China, and they could play a role in reducing the number of emerald ash borers that continue to affect ash trees after the first mega-wave of ash borers passes through an area. There's a video that gives a brief history of EAB (complete with darkly evocative sound effects) and then describes three parasites of EAB that were found in China and are now being released in the U.S. after thorough testing.

There's a bit of good news. Valued ash trees along streets or in yards can be spared, for a price. And wild ash trees do not disappear altogether. We found 20 foot tall ash trees making a go of it, here and there. Dave says that 80% of the EAB larvae get eaten by woodpeckers. It's still a mystery how the woodpeckers are able to locate the larvae under the bark with such consistent precision.

Here's a young ash showing the outer symptoms of EAB attack. I would speculate that, once the native and introduced parasitic wasps become widespread, they in combination with woodpeckers could allow ash trees to persist in Princeton, though perhaps few would grow to maturity unless regularly treated with systemic pesticide.

While we were walking around, Dave found one of the signs he and other researchers had placed around the park years back to explain why they happened to be pulling the bark off of thousands of trees in a public park.

Click on the photo to make it more readable.

Here's an ash tree showing signs of dieback on the upper right--likely to be a common sight in Princeton in coming years.

HOW TO SAVE SPECIMEN ASH TREES

It's important for those who have ash trees in their yards to know that those trees can be protected with systemic pesticides. Not all the available pesticides are equally effective, however. Though imidicloprid is being frequently recommended locally, the experts in other states that I've spoken to have all recommended emamectin benzoate (brand name Tree-Age, or Arbor-Mectin).

Page 15 of this document is very informative, and says the emamectin is the most effective and longer lasting, while warning against use of imidicloprid on larger trees. Dave says that the EAB expert Deborah McCullough recommends emamectin, which is supported by this article about communities in Minnesota. The article is very optimistic about saving some ash trees, and offers this interesting approach:

"Burnsville is so sold on that idea of saving trees, rather than cutting them down, that it plans to encourage residents to treat their trees by extending to them the rates the city receives for pesticide injection. "

Curtis Helm, a former Princetonian and currently an urban forester in Philadelphia's Parks and Rec department, advises against using imidicloprid on trees larger than 16" diameter. He says Philadelphia is treating 1000 ash with Tree-Age.

In a previous post on the subject, I included notes from an extended conversation with Donald A. Eggen, Division Chief of Forest Pest Management Division of Pennsylvania. He, too, strongly recommended Tree-Age rather than products that use imidicloprid.

The emamectin benzoate, last time I checked, was more expensive, which may explain the local preference for imidicloprid, but that cost differential is reduced when the frequency of application is considered.
Note: The Arbor-Mectin formulation is said to be absorbed into the tree more quickly than Tree-age, and therefore can be less expensive to apply. Both use the same active ingredient.

Any decision about how Princeton should proceed with pesticide applications (some homeowners have already begun applications, given that EAB has been discovered 25 miles north of here), should weigh heavily the input of those in Michigan, Pennsylvania and elsewhere who have benefited from years of experience.

Princeton Expected to Lose Its Ash Trees

This is a towering white ash tree, one of thousands in Princeton, and for as long as anyone can remember, it has grown "real good for free", as Joni Mitchell might say. As with the clarinet player in her song, playing for free on a street corner, people pass it by without a thought, while it quietly supplies beauty and abundant ecological services--shade, cooling, habitat, oxygen, carbon sequestration--all rendered at no cost.

That's about to change. Four years ago, I wrote on this blog:

"In Princeton, we will over the next decade likely witness a dieoff approaching the scale of the chestnut and elm dieoffs of the 20th century, as the emerald ash borer, which hitch-hiked to Michigan from Asia in wooden packing crates, continues its spread eastward." 

It doesn't take any great clairvoyance on my part to see the future. I had once lived in Ann Arbor, MI, which had to cut down 10,000 ash trees at a cost of $5.8 million.

Living in Princeton, then, is like having traveled back in time. Knowing what's in store, what's been sweeping eastward from the midwest, makes me appreciate more what we still have. I pause more than I might otherwise at the sight of an ash, particularly in the fall when they change color. The halcyon moment for me with ash trees will always be the time, long before the emerald ash borer came on the scene, when I drove north in Michigan to play for a wedding that was perfectly timed with the fall colors. Sugar maples dominated with their radiant orange and gold. Sumac made horizontal strokes of brilliant red. And the uncanny mix of yellow and purple in the ash trees was so strong it seemed to vibrate. We were paid for our time, but they let us play the jazz tunes we love, outdoors, overlooking a glorious valley of color. Our singer's rendition of Make Someone Happy was so full of buoyancy and conviction we knew we had found the meaning of life. If a composer like Scriabin can see color in music, then surely there was music in the colors of the north woods that day, the trees playing an ancient symphony freely given, filling us with enough color to last us through the long Michigan winter

This spring, the emerald ash borer, known unaffectionately by its acronym, EAB, was finally found in NJ, 25 miles north of Princeton, in a parking lot next to Patriot Stadium in Bridgewater. Though those of us who knew it was coming have a head start on grief, the official announcement on May 21st still had an emotional impact. This link used to show New Jersey as free of EAB, but essentially surrounded by infestations in bordering states. Now NJ has been added to those with EAB. It may have flown in on its own, from NY or Pennsylvania, or it may have been transported in firewood. None have shown up in traps set in Princeton, but the traps are an imperfect test of their presence.

Princeton's battle with the beetle will be expensive. The strategy cannot realistically be to win, but to cushion the blow to canopy and pocketbook. Any view more optimistic than that veers into wishful thinking. In the twelve years since it was first identified in Michigan, neither white nor green ash has shown resistance to the insect, and no controls are poised to save the day. We may save some of our ash trees with systemic insecticides, at considerable expense, but far more will be lost to a diminutive beetle that no one noticed in Michigan until it had become to entrenched to eradicate. And Princeton has a lot of ash to lose, it being our most numerous tree. Arborist Bob Wells' recent inventory identified 2200 white and green ash trees along the streets, plus the uncounted thousands in our parks and woodlands. 

The strategy for dealing with the invasion, which could arrive in Princeton in a year or two, or could already be here but undetected, will likely involve chemical treatment to protect the finest specimens, and beginning to cut down other ash even before they show symptoms.

There are chemicals that can be used to save individual trees. As a proactive measure, Princeton University began treating its most valuable ash trees two years ago. Choosing which insecticide to use involves tradeoffs. Imidicloprid is less expensive, but is injected into the soil around it rather than directly into the tree. Because the compound is toxic to pollinators, it should not be injected where flowers are growing beneath the tree. The herbaceous plants will absorb the chemical and transfer it to the pollen in their flowers, where the pollinators will be exposed. Other options can be found in the extensive notes below.

Two things are particularly upsetting about the arrival of the emerald ash borer. Of course first and foremost is the loss of a tree species and all the beauty and services it has been providing for free. The other is New Jersey's incredible lack of preparedness. Composting centers are already overwhelmed. Trees make an excellent fuel--one of the few ethical forms of energy we currently have available to us, since wood's carbon comes from the air rather than from underground sources. The technology is available to cleanly run cogeneration plants with wood for fuel. If the state actually is preparing for what one arborist called "ten years of mayhem", it's being done very quietly. Chances are, New Jersey will only start reacting once the devastation begins, even though it had ten years to prepare.

The recurring lesson is of the abundant services and beauty nature gives, every day, none of which are entered into our economic calculations, and the increasing vigilance and stewardship required to guard those gifts as global trade increases the pace of change. Below are my collected notes on the coming invasion, including an extensive phone conversation with Donald Eggen, division chief for Forest Pest Management in Pennsylvania. 

Notes from a conversation with Donald A. Eggen, Division Chief of Forest Pest Management Division. (These notes were rapidly written, but are my best rendering of what Eggen said.)

EAB attacks trees as small as 1" in diameter.
The insects start at the top of the tree and work down.

Expansion of EAB into new areas
In 2013, PA documented EAB in 16 new counties without even looking very hard
The Louisville Slugger baseball bats are made out of ash harvested in northern PA. EAB is now moving into that area.
Traps for detecting EAB in an area don't work very well. Their odor imitates a stressed tree.

In a given area:
EAB doubles each year. If 16% of trees affected, the next year there will be 32, then 64, then all. It can sweep through a town in five years. (sources on web suggest more like ten years--perhaps it takes a few years to get to 16%, and then a couple years to kill those that are last to be attacked).

Assessment of a tree
Take DBH (DBH (diameter at breast height) is a poor measure. Bigger trees need more juice.)
If 70% of crown looks good, then tree could be saved
If it dies, it becomes a hazard tree
Don't treat if more than 30% in decline. Insect damage can't be repaired. Most ash in decline, even without EAB, due to winter storms, wet weather, all of which, if it's a street tree, brings out root ball problems left over from improper planting. Kill the roots, kill the tree.

Strategies
Options are to treat, to remove, or to remove and replace.
Don't delay on treatment. Do most critical trees in first year. Spread the cost out.

He mentioned Chris Sadoff at Purdue, and I later found this, which is one of many such documents on the web to help with decision making: http://extension.entm.purdue.edu/EAB/PDF/NABB_DecisionGuide.pdf

Treatment: Recommends Tree-age (Emamectin Benzoate), a play on the word "triage". Not available to homeowners, it's restricted use, and must be applied by professionals. It's more expensive than another treatment with various names such as Merit, but has advantages in that it is injected directly into the tree. The injection point is at the base of the tree, where it flares out just above the ground. This is where the sapwood is thickest. The product is made by Arbor Jet, and applicators should undergo training through Arbor Jet. There is reason to believe that it will last longer than two years, possible 4 or more.

Merit, as with other similar products whose active ingredient is imidicloprid, is injected into the soil around the tree. If the soil is compacted, the uptake could be slower. Something called Safari is sucked up faster by the tree than Merit, but doesn't last as long (?). Both Merit and Safari protect the leaves well. A product called Xytec has to be applied every year.

Timing
With Tree-age, treat late May through June. A cloudy day with a little breeze is best. (presumably when a tree is translocating upward most effectively).

Cost
Ash can be more costly to remove than to treat. If they die, they become brittle very quickly, which makes them more dangerous to work on. Some arborists refuse to go up in the trees if they have become brittle. An increase in accidents has been documented. The trees can also become weak at the roots and topple over at the base.

Chicago is treating tens of thousands of ash, at a cost of $1.4 million/year.
The plan is on the website. Westchester, PA has a 10 year plan that includes cost.

Other insects/diseases
Asian Longhorned Beetle (ALB) in Wooster, MA, big infestation. ALB has gotten into the woods, which is bad because it doesn't kill trees in the woods and therefore is hard to find. Not as good a flyer as EAB, so slower to expand territory.

Black walnut disease found in Bucks County, contained apparently.

(End of Eggen notes)

__________________________________________________

SYMPTOMS OF EMERALD ASH BORER (taken from the web)

1. D-shaped exit holes – 1/8” inch holes left after adults exit the tree

2. Bark splits – vertical splits in the bark

3. S-shaped feeding galleries – can only be seen when bark is scraped or in bark splits

4. Woodpecker damage – missing or discolored bark beginning at the top of the tree

5. Crown Dieback – foliage at the top of the tree may thin or discolor

6. Epicormic sprouting - shoots of leaves growing from the trunk

The New York Times ran an article on emerald ash borer, featured in a talk in Princeton by the Times science editor that same day.

Here's an article that claims that woodpeckers can play a role in controlling EAB. I'm skeptical.

I also found on the web a city that was paying $90/tree for treatment using Tree-age

Interestingly, ash continue to sprout in the woodlands in Ann Arbor, and can grow to 6 inch diameter, but the chances of their growing to maturity are slim.

Some sources on the web suggest that once EAB  passes through and attacks all the trees there are to attack, then ongoing treatment costs for those trees saved will come down somewhat.

Update: A short video on a parasitic wasp being introduced in Maryland to help control the EAB. Sounds like it could potentially help in the longterm, but is described as "a drop in the ocean", given the vast numbers of EAB compared to the few parasitic wasps released.

Holden Arboretum Studies Resistant Beech and Ash Trees

Herein lies a post about the long, patient work that begins when something goes wrong with the world. With the introduction of beech leaf disease into North America, things have gone very wrong. Another noble, native tree species, towering and strong, is proving no match for a microscopic nematode. When this happens--yet another example of collateral damage from international trade--scientists mobilize to seek understanding and possible remedies.

In recent blog posts about beech leaf disease, I've mentioned Holden Arboretum. Holden happens to be located east of Cleveland, close to where the disease was first noticed back in 2012. Visiting family in Cleveland this summer during a band tour, I reached out to Holden staff to see if I could stop by to witness their research on the disease. 

Tucked behind some 3000 acres of gardens and ponds, forests and fields, is a research station where Holden is devoting staff and greenhouses to a collaboration with the U.S. Forest Service and others to test resistance not only beech leaf disease, but also to the introduced insects that have decimated two other native trees--ash and hemlock. 

I learned primarily about their research on beech and ash trees.

AMERICAN BEECH

Where did the nematode that causes beech leaf disease come from? According to Rachel Kappler, Holden's Forest Health Collaborative Coordinator, who generously came in on a Saturday to give me a tour, they have identified the island in Japan from which the nematode came. It was not a species from Asia's mainland. 

Holden's main endeavor is to seek out beech that show some resistance to the disease, and test that resistance. 

Rachel first grows seedlings that can be used as root stock for these tests. The root stock serves as the bottom half of a graft.

When trees are found that have lingered in the landscape while others succumb, Rachel then grafts cuttings from these "suspiciously healthy" trees onto the prepared rootstock. 

Once the grafts heal,

the trees can be tested for resistance. Measured numbers of nematodes are applied to the buds, documented with colored tags, and the tree's resistance to the nematodes is then observed.

The nematodes are small enough to enter the buds between the overlapping bud scales. The tiny worm-like creatures inhabit the leaves all summer. Then in fall, exiting the leaves through the stomata--the openings on the undersides of the leaves through which the tree breathes--the nematodes transfer to the new buds to overwinter.

Each step in the process of testing resistance takes time and consistent attention. Rachel says some promising means of speeding research are in the works. Promisingly resistant trees can be propagated using only their leaves. The leaves are cut, a particular root hormone applied, then the leaf is stuck in soil medium to grow. This approach could potentially avoid the need to grow root stock, grafting, and the time it takes for grafts to heal.

As for treatments for the disease, she says soil applications of phosphite have mostly been experimented with on smaller trees because it's easier to study at these smaller scales. Similarly, using chemical sprays on the trees' foliage requires just the right timing, and a thorough coating, which makes larger trees very difficult and expensive to spray. They are experimenting with pruning to allow better air circulation and thereby reduce the moisture that the nematodes like.

ASH TREES

Research on resistant ash trees is a little farther along. Rachel showed me a grove of young green ash--protected by a deer fence--that are being tested for resistance to the Emerald Ash Borer (EAB), which spread through Ohio nine years before Beech Leaf Disease. This is the same introduced insect that has decimated Princeton's ash trees.

Rachel explained that the ash can defend themselves from the burrowing insects in three ways. One is a blockage that prevents entry. Another is to react by building a wall around an ash borer that has gotten in under the bark. Another is to somehow deprive the ash borer of nutrition, so that it becomes stunted. 

Sticky boards are used to monitor the presence of Emerald Ash Borers at the site.

When I told her that I had only seen one adult Emerald Ash Borer in my life, despite the hundreds of millions of ash trees killed, she pulled one off of the sticky board.

In this closeup, the Emerald Ash Borer is on the left; a native ash borer, far less destructive, is on the right. Though they are similar in appearance, it's the difference in behavior of the introduced species that has proven lethal.

She said that ash trees become vulnerable to EAB attack fairly early in life, certainly under ten feet high. While some of the ash trees being tested in the grove are dying due to EAB (perhaps these are the controls in the experiment), 

many are doing well, showing some degree of resistance. 

The green ash that have proven resistant to the EAB must not only be able to survive at low EAB levels, but also when the Emerald Ash Borer is present in high numbers. Rigorous testing helps avoid later marketing an ash variety that ultimately could prove vulnerable. 

This scar is evidence of an inner struggle by the ash to fend off the borer. The tree tries to build walls around the EAB larvae. 

Rachel described an autoimmune reaction, observed in black ash up north, in which the tree is too aggressive in blocking off passages, interfering with its own circulation. 

She talked about the physical aspects of doing research on trees and their pathogens. The wooly adelgid that plagues our hemlocks is hard to study, in part because it can be hard to apply the soft insect to test trees without squashing its soft frame, so they use its eggs. Nematodes are much easier to count and apply to branches.

Expanded greenhouses suggest Holden is expanding its efforts to nurture trees resistant to imported insects and disease. 

One bonus from my visit was that Rachel took an interest in our efforts in Princeton to bring back the native butternut (Juglans cinerea), and has put us in touch with someone studying the species.

If, as beech leaf disease takes its toll on beech trees in Princeton, we see some trees that "linger" and remain "suspiciously healthy," we'll want to notify Holden Arboretum, to aid their ongoing search for resistant trees. 

A thunderstorm prevented me from exploring the many gardens at Holden that day, including a treetop walk and tower. And then there's the Cleveland Botanical Garden closer into town, with which Holden recently merged. These are some good botanical destinations in Cleveland, with a mission that extends far beyond the city, and an engaging origin story.

More on Emerald Ash Borer

While in Chicago recently for a family reunion, I stepped out on the back patio of my niece's apartment in Hyde Park, looked up, and saw that a neighbor's tree was dying. The thick, opposite twigs suggested ash, and the loss of most of the crown, with only a few lower branches still green, suggested that Emerald Ash Borer (EAB) has made it to Chicago.

In a nearby Chicago park, I found the characteristic D-shaped exit hole (the native ash borers make a round exit hole).

New Jersey had been exceptional in being free of emerald ash borer, until last year when it was spotted in Somerset, then later in Mercer County. This year, at the May meeting of the Princeton Shade Tree Commission, council member Bernie Miller sounded reasonably sure he had seen one in his yard.

Our town arborist, Lorraine Konopka, has placed two traps on the east and west side of town--one at Valley Road, the other at Marquand Park. The traps contain a pheromone that will attract the insect if it happens to be nearby. Whether or not the traps catch any insects, it's best to assume that EAB has made its way to Princeton, and begin considering which ash trees to treat. It would be nice to think that some ash trees will resist attack on their own, but that hasn't been the experience elsewhere, as far as I know.

Below is info on treatment options from a previous post, along with some related links:

HOW TO SAVE SPECIMEN ASH TREES
It's important for those who have ash trees in their yards to know that those trees can be protected with systemic pesticides. Not all the available pesticides are equally effective, however. Though imidicloprid is being frequently recommended locally, the experts in other states that I've spoken to have all recommended emamectin benzoate (brand name Tree-Age, or Arbor-Mectin). 

Page 15 of this document is very informative, and says the emamectin is the most effective and longer lasting, while warning against use of imidicloprid on larger trees. Dave says that the EAB expert Deborah McCullough recommends emamectin, which is supported by this article about communities in Minnesota. The article is very optimistic about saving some ash trees, and offers this interesting approach:
"Burnsville is so sold on that idea of saving trees, rather than cutting them down, that it plans to encourage residents to treat their trees by extending to them the rates the city receives for pesticide injection. " 

Curtis Helm, a former Princetonian and currently an urban forester in Philadelphia's Parks and Rec department, advises against using imidicloprid on trees larger than 16" diameter. He says Philadelphia is treating 1000 ash with Tree-Age. 

In a previous post on the subject, I included notes from an extended conversation with Donald A. Eggen, Division Chief of Forest Pest Management Division of Pennsylvania. He, too, strongly recommended Tree-Age rather than products that use imidicloprid.
The emamectin benzoate, last time I checked, was more expensive, which may explain the local preference for imidicloprid, but that cost differential is reduced when the frequency of application is considered. 

Note: The Arbor-Mectin formulation is said to be absorbed into the tree more quickly than Tree-age, and therefore can be less expensive to apply. Both use the same active ingredient. 

Links to news stories about emerald ash borer being found in Mercer County are here and here.

There's also evidence from Yellow Springs, Ohio, that another native related to ash trees, the fringe tree, can be attacked by emerald ash borers. I've only seen fringe tree once in the wild, in a nature preserve I helped create in Durham, NC, though it is becoming more common as a beautiful ornamental shrub/tree.

Trouble For Princeton's Trees

To inoculate you for the news carried in this post, I'd like to point out that wishful thinking is not the same as hope. In fact, to the extent that it postpones action, wishful thinking can be thought of as the enemy of hope. Bad news is much more easily accepted if we feel confident in our capacity to work together as a community to respond.

Princeton has a real challenge ahead if it is to keep its protective canopy of trees in coming decades. There are the losses in recent years due to storms like Hurricane Sandy, the ongoing attrition as some pin oaks and red oaks succumb to Bacterial Leaf Scorch, and then there is the gathering storm just to our west of the emerald ash borer. Through a recently completed tree inventory, Princeton can now look at the numbers, and they don't add up--the number of trees likely to be lost dwarfs the number of trees being planted.

Doing the Math

Here are the numbers, rounded off for easier math, as presented by Bob Wells of Morris Arboretum, who directed the inventory and integrated it with an earlier survey of borough trees done by Jim Consolloy. These are only the trees growing in the street right of ways. Trees in parks, preserves, and on private property are not included. Of Princeton's 19,000 street trees, 3000 are in poor condition--unlikely to live beyond the next five years. Another 6000 are in fair condition, with an estimated life expectancy of 5-15 years. Even those trees in good condition are threatened by a growing collection of invading insects and diseases, along with the increasing weather extremes associated with climate change. For instance, some of Princeton's 1400 pin oaks and red oaks will continue to be lost to Bacterial Leaf Scorch.

Compare those numbers with the current replacement rate. Princeton purchases and plants about 60 trees each year along the streets. Its tree crew takes down about 250 trees each year in parks and along streets. The numbers offered up by the tree inventory estimates the annual loss of street trees to be a minimum of 600. By this math, we will be losing ten trees for every one being planted. And this doesn't even take into account the imminent arrival of the Emerald Ash Borer.

http://www.tinleypark.org/index.aspx?nid=648

Emerald = Less Green

Perhaps most worrisome is the looming threat to Princeton's most common tree, the ash. We can expect to lose most of our 2200 white and green ash trees along the streets in coming years, plus the tens of thousands in our woodlands. The culprit is the emerald ash borer (EAB), an insect that hitch-hiked to southeastern Michigan in wooden packing crates from China, then proliferated to kill 50,000 trees before anyone knew what it was. Since its identification in 2002, EAB has been radiating out across the midwest, killing tens of millions of trees, including a relentless spread eastward through Ohio and Pennsylvania to the border with New Jersey. A map at this link shows New Jersey essentially surrounded by infestations in bordering states.

As chance would have it, the original EAB infestation occurred just north of Ann Arbor, MI, where I used to live. The city of 100,000 had to spend $5.8 million removing 10,000 trees. Interestingly, ash continue to sprout in the woodlands there, and can grow to 6 inch diameter, but the chances of their growing to maturity are slim.

Princeton has dealt with threats to trees in the past. A bacterium called Bacillus thuringiensis (BT) has been used to reduce the impact of gypsy moths. According to Greg O'Neil, Princeton's arborist, the wooly adelgid's attack on our eastern hemlocks was slowed down by pesticide, after which the pest appears to have "cycled through", allowing many hemlocks to survive.

There is, however, no known control for emerald ash borer other than individually treating each tree, and even then the results are mixed. As an added complication, Imidacloprid, the most frequently mentioned systemic insecticide for protecting ash trees, may be contributing to the decline of honey bees.

What To Do

The sooner we acknowledge the depths of the challenge we face, the more proactive we can be, and the better the prognosis for Princeton's tree canopy. There are a number of actions that can be taken. Treatment for ash trees that are particularly cherished is best undertaken before the emerald ash borer arrives. To better spread the work of removal over a number of years, some of the younger or less healthy ash trees can be taken down and replaced with another species before the invasion hits. The municipality should at least be planning for the extra staff needs and the seven figure expense coming down the pike.

The big question is how to replace so many trees with a limited budget. The more gaps in the street canopy, the more pavement is exposed to the sun, which through the "heat island effect" causes the town to be hotter than it need be in the summer. At $200 a piece, new trees aren't cheap, and then there's the planting and followup care to insure they survive.

One approach I'm exploring, as a member of the Princeton Shade Tree Commission, is transplanting "volunteer" trees that sprout in people's yards. Some species are more appropriate than others, and determining where to plant them along the street requires some guidance. Perhaps we can come up with a guide, and motivated neighbors could take initiative in their neighborhood to identify gaps and work with willing homeowners to get trees planted in an optimal place and manner along the street. Given the infinite reasons that can be summoned for inaction, such an approach will only work if people see how their own needs can be met by participating in the collective endeavor of shading our streets.

For me, the hope lies in the growth force and the natural affinity people have for trees. It's remarkable how quickly the red oak in this photo, which sprouted on its own in my next door neighbor's yard not that many years ago, has grown large enough to cast much-needed shade on our driveway.

Neighbors a couple doors down have transplanted volunteer trees to key spots in their yard--to shade the house, provide habitat for birds, and provide buffer from the street. After just a few years, they are robust young trees--a white oak, pin oak, American elm and tulip poplar. Another friend is growing a pawpaw and a fig in a sunny spot in their backyard--going for food rather than shade.

Each kind of tree has its strengths and potential drawbacks and vulnerabilities, but after years in which Princeton's landscape was dominated by mature trees, it's refreshing to see young ones coming on the scene, filling the voids, reaching for the sun.

Related to this, the opening reception for an art exhibit entitled "The Fallen and Unfallen: Trees in Peril" is Nov. 1 at the DR Greenway, 5:30 to 7:30. More info here. With paintings and photographs, it celebrates trees while also identifying some of the threats they face, in little snippets of info like this one.

Seeking "Lingering Trees"--Some Hope for Ash and Beech Trees

Most people attentive to nature are aware that Princeton has lost nearly all of its native ash trees over the past decade, and is now poised to lose its native beech trees as well. These are only the most recent losses due to assorted introduced insects, nematodes, and diseases against which our native trees had not evolved resistance. Also gone from the canopy over the past century are American chestnuts and American elms, with bacterial leaf scorch also taking a toll on red and pin oaks. As additional organisms enter the country due to an appalling lack of biosecurity, other species are threatened. 

What is there to do other than mourn, and mourn again, with each new wave of devastation? 

One answer to that question may be: Keep an eye out for "lingering" trees. It would be easy to assume that all our native ash, not having co-evolved with the Emerald ash borer (EAB), would be equally defenseless as the introduced larvae eat through the cambrium, cutting off the tree's circulatory system. But an initiative in Ohio has shown this not to be entirely true. Jennifer Koch, a research biologist with the USDA Forest Service, has been leading an effort to find "lingering ash", that is, mature ash that survive while others all around them succumb. Some ash that she and others have found have natural defenses that kill 20-45% of the larvae that bore into them. A very few trees kill 100% of the invading larvae. 

A very watchable video features Jennifer Koch, and also Holden Arboretum's Rachel Kappler, telling the 
story of ash lost, lingering ash found, and the effort to increase resistance among lingering ash through research and breeding programs.

One particularly impressive slide in the presentation showed how the resistant trees are able to stop the invading larvae before they do damage to the tree. 

 
Here are some of my notes from the video:

• Ash wood is/was used for bats and guitars
• Native ash species in our area: White, green, black, pumpkin
• 300 million acres of black ash-dominated forest in Minnesota could be lost (apparently no other tree species can survive in those wet areas)
• green ash is an important riparian buffer species in the plains states, hard to replace
• The lingering ash are found individually or in clusters, e.g Swan Creek, Oak Openings Park, near Toledo, 108 out of 11,000 had healthy canopies. Two specimens had no evidence of attack. Most resistance is partial, but resistance can be increased through breeding
• greenhouse tests can reduce the amount of land/labor needed for field tests
• resistance is inherited, though uneven

A central point these researchers make is how very limited is the area they have surveyed for lingering ash--only a small area near the Ohio/Michigan border. They call for similar initiatives in other parts of the country. 

That's where we come in, as keen or at least intermittently keen observers of the landscape through which we walk. It's important that any tree we believe to be lingering be a mature, wild tree--not a cultivar in a planted landscape--and that it be a tree that has weathered the massive wave of EAB over the past ten years, remaining green while others nearby have succumbed. Photos of lingering ash, and one story of their discovery, can be found at this link. 

A brief mention of the various species of ash: I associate white ash with higher ground and grander specimens found or once found around town. Green ash are less statuesque and more associated with wetter ground. Black ash I think of as growing, or having grown, in swamps, such as at Rogers Refuge in Princeton. The Ohio initiative is apparently finding most success with resistant green ash, though the video mentions lingering white, green, and black ash having been found in NY state.

In addition to the info below, there's also anecdata.org--a platform where citizen scientists can set up reporting initiatives.

This keeping an eye out for "lingering" ash can also be applied to other imperiled species in our area. The Ohio researchers request that people report lingering American beech, hemlock, and American elm as well. 

Related posts:

Emerald Ash Borer in Princeton

Beech Leaf Disease Sweeps Across Princeton

Holden Arboretum Studies Resistant Beech and Ash Trees

Emerald Ash Borer Informational Meeting Tonight

Below is information from the Princeton Shade Tree Commission website about the meeting tonight at town hall.

I've written from many different angles on the subject of Emerald Ash Borer (EAB) in recent years, such as this one. Type "emerald" into this website's searchbox and various posts will come up. The photo shows the size of the insect, and the "D"-shaped exit holes.

A very experienced arborist I spoke to this week told me that he is injecting emamectin benzoate--the active ingredient in Arbor Mectin and TreeAge--for individual or specimen trees, and using imidachloprid where there are dense stands of ash that the homeowner wishes to save. Emamectin benzoate is more expensive but is more effective and lasts longer.

There are no easy answers as to whether to try to save an ash, take it down now, or keep it until it succumbs. All have a financial cost. With 2000 ash trees in Princeton's public right of ways, and many thousands more in parks, preserves and public lands, this little insect introduced from Asia via shipping crates will have an ecological impact on our open space lands and cost Princeton and its residents millions of dollars. Due to the transport of species from one continent to another, all the free ecological, aesthetic, and cooling services ash trees have provided through history will now have a price tag.

Info on the meeting below:

IMPORTANT MEETING ON THE EMERALD ASH BORER: PRINCETON WILL HOST AN INFORMATIONAL SESSION ON PRINCETON'S ASH TREES AND THE EMERALD ASH BORER, THURSDAY, JUNE 23, 7 PM, AT THE PRINCETON MUNICIPAL COMPLEX, 400 WITHERSPOON STREET. EVERYONE IS WELCOME.

Beech Leaf Disease Sweeps Across Princeton

Princeton is losing its beech trees.

We were feeling celebratory, having just completed a successful corporate workday in Herrontown Woods, when I happened to pass by this small branch of a beech tree along the red trail. The leaves were strangely contorted, with dark green stripes. I had heard distant rumblings about a disease of beech trees, but had managed to keep my head in the sand until that moment. 

Back home, diagnosis was but a google's search away. Similar images popped up on the screen, along with the name: Beech Leaf Disease. Tree maladies typically come with an acronym. Emerald ash borer is EAB. The dreaded asian longhorned beetle, which they've had some success keeping from spreading across the eastern U.S., is ALB. The Bacterial Leaf Scorch that afflicts pin and red oaks is BLS. Now there was a new one: BLD. 

For those unfamiliar with the American beech (Fagus grandifolia), it's a native tree related to oaks and chestnuts, with beautiful smooth gray bark. They can get very big and live for centuries. Thousands of them grow in Princeton, in the preserved forests along the Princeton ridge and on slopes above the Stony Brook. 

The "grandifolia" in the latin name refers to the leaves, which are larger than the leaves of European beeches. This photo shows some healthy leaves (on top) and the curled, darker green leaves that have been contorted by nematodes overwintering in the buds. Beech leaf disease is caused by these nematodes--tiny worms spread by birds or the wind. 

Viewed from beneath, the infected leaves show a curious striping of dark and light green. 

During a subsequent hike in Autumn Hill Reservation, I was astonished to find nearly all the beech trees affected--their leaves contorted, their crowns beginning to thin. Beech in Rogers Refuge are showing symptoms, and Mountain Lakes preserve is reportedly also affected. According to online sources, essentially all of our beech trees will be dead within ten years. The news comes exactly ten years after the first emerald ash borer was found in New Jersey, with the skeletons of ash trees still haunting our woodlands.

According to this map, on the Holden Arboretum website, the disease was first spotted near that arboretum in Ohio in 2012, and has spread in all directions, most rapidly eastward.

According to the Maryland Extension website, the microbe causing the disease is Litylenchus crenatae mccannii, a subspecies of a nematode found in Japan. As one would expect, the only beeches resistant to this particular nematode are those that coevolved with it in Japan. 

The Holden Arboretum website mentions a chemical treatment that is being tested. It is a compound that is sprayed on the tree in the fall just as the nematodes are moving from the leaves down into next year's buds. Unfortunately it is highly toxic. The snail's pace of tree research compared to the rapid development of Covid vaccines caused one friend to ask, "Where is science when we need it?" 

The loss of a tree species from the canopy has all sorts of impacts on wildlife. Ash, elm, and maples bear abundant seeds early in the season to feed on. Two of those three have been largely lost. Nut-bearing trees provide food in fall and winter. Gone from wildlife diets are chestnuts, bacterial leaf scorch is reducing oak production of acorns, and it now looks like beech nuts will become very rare. Websites detail the ecological web of connection and dependence that is unraveled by the loss of a tree species. 

A post last year by the Brandywine Conservancy in Pennsylvania provides a particularly chilling description of what is in store for eastern forests:

"As the disease progresses, leaves will become smaller in subsequent years, and it will seem like autumn in the summer as infected leaves brown and fall from the tree, resulting in thinned crowns and branch dieback. Eventually, BLD will cause beech trees to abort their buds, leading to the death of the tree. Young beech tree saplings die within 2–5 years of infection, while mature trees live a bit longer. Death from BLD is likely accelerated in beech trees stressed by drought or Beech Bark Disease, which is a different infection that involves scale insects and fungi."

Here's a writeup I found on beech bark disease, which also poses a mortal threat. 

I encourage people to visit favorite beech forests in the area sooner rather than later, to appreciate the now threatened beauty of this singular tree. Over the next few years, if you are fortunate enough to find one that remains healthy while others around it succumb, you should let people know. The Holden Arboretum site provides someone to contact.

Yesterday evening, I visited the fabulous congregation of European beech off of Elm Lane on Constitution Hill in western Princeton. The many trunks appear to all come from the original massive trunk in the middle. 

Seen from a distance, they appear to be separate trees, but more likely were either branches that touched the ground and took root, or sprouts from the original tree's massive root system.

You can see how some of the trunks still have a sort of navel, where the original branch from the "mother tree" was cut off.

Its leaves, smaller than those of the native beech, were  showing early signs of the disease.

Some of Princeton's most spectacular native beech trees grow in the Institute Woods. That will be my next stop--that and a hidden valley between the Princeton University chemistry building and Washington Road, where I found a mixed forest of 200 year old trees, part of the great American forest cathedral that, in unspeakable sadness, loses its towering pillars, one by one.

Here is how I concluded a recent letter to the editor in the Town Topics: 

Outrage is often triggered by the intentional cutting of trees. The highly visible spotted lanternfly caused a stir, yet has proven relatively innocuous. The biggest threats we face are neither visible nor intentional. The emerald ash borer is hidden behind bark. Nematodes are microscopic. Our machines’ climate-radicalizing carbon dioxide? Unintended and invisible.

There is so much joy still to experience, for me particularly in Herrontown Woods, and yet in the larger workings of the world, so much to grieve.