Posts Tagged Green Ash
Those of you who have read this blog for a while may remember when I first wrote about the invasive non-native insect called Emerald Ash Borer here. This insect species is killing almost (maybe all) ash tree species in North America — no joke. It started in areas like Canada and Michigan, and has been marching steadily southward ever since. Its occurrence is widespread in North Carolina. Dr. Kelly Oten, Forest Health Monitoring Coordinator for the North Carolina Forest Service, told me that confirmed sitings are reported for every county around me. The closest infestation she knows of is about 10 miles north of my five acres.
I had read about an experimental program Dr. Oten’s office is using to combat the Emerald Ash Borer (EAB) — the release of a parasitic wasp species native to the same part of Asia where EAB evolved. I believe the wasps used in NC parasitize EAB eggs by laying their own eggs inside EAB eggs. A couple of wasp species that parasitize EAB larvae also exist, as described in a US Forest Service publication on EAB biocontrols here.
I assumed that my little five-acre patch of Piedmont would be too small for this experimental wasp release program, but a forester friend of mine encouraged me to give Dr. Oten a call, so I did. I was delighted to discover that Dr. Oten was interested in the stand of 37 mature Green Ash trees growing on the floodplain portion of my land. However, she cannot release wasps unless she is certain the EAB is present on my land, because the wasps will die without a food source.
I have seen no evidence of EAB damage in my ashes <knock wood>, such as crown dieback and a yellowing of leaves (Here’s a link to a PDF from the Canadian Forest Service containing everything you need to know about detecting EAB damage.), so Dr. Oten suggested that we set up a couple of EAB traps at the appropriate time. That time is early April, because that’s when EAB egg-laying occurs, and it is EAB eggs that the experimental wasps look for to parasitize.
On the morning of April 11, Dr. Oten arrived with two traps to hang on a couple of my ash trees. The traps are shipped flat in pairs that are stuck together by the sticky fly-paper like glue used to snag passing EABs. In the above photo, she has successfully pulled the two purple traps apart and has begun to fold the one she is holding so that the sticky glue is on the outside of the three-sided trap. The traps are purple, she told me, because research shows this color attracts EABs most effectively, perhaps, it is theorized, because young ash leaves often possess a purplish hue.
Besides the EAB-preferred purple color, traps also contain a bag of scent lure that is hung inside the trap. Dr. Oten is holding one of those bags in the above photo (click on any photo to see a larger version). The scent emulates the smell of an ash tree in distress. Many studies have confirmed that plants engage in sophisticated chemical warfare with their insect enemies. In many plants, when a plant is under attack, it emits a scent signifying its distress, which in turn stimulates nearby plants of the same species to begin producing chemicals that may help them repel invading insects. This doesn’t work for the ash trees with EAB, because North American ash trees did not evolve with this insect; thus, they have not developed any defenses against EAB attacks.
After she attached lure bags to the center of the EAB traps, Dr. Oten used the long extension pole in the photo to attach the traps to sturdy horizontal branches on two ash trees at opposite ends of my floodplain. This turned out to be trickier than you might think, because my canopy-size ash trees don’t possess many horizontal branches within reach of the pole. Dr. Oten’s first attempt to hang the trap was unsuccessful; the sticky trap fell into a stand of bladdernut shrubs, thus becoming adorned with bits of bladdernut leaves and flowers. Her second attempt with a different tree was successful.
In the second photo above, you can see bits of bladdernut leaf and flower stuck to the trap. Dr. Oten said this will not interfere with the trap’s effectiveness in luring EABs.
Next, we slogged through the mud to the far side of my floodplain, where Dr. Oten selected a second ash tree suitable for trap-hanging. This operation went more smoothly than the first, and the trap was soon hung.
Dr. Oten explained that EABs are actively flying and egg-laying in my area from early April until about June. She plans to return to my floodplain in about four weeks to inspect the traps for EABs. If she doesn’t see any, she will add fresh lure bags and return in another four weeks. If no EABs are found on the traps during that time period, it is less likely — but not impossible — that EABs have found my ash trees — yet. If she does find EABs stuck to the sticky glue on the purple traps, she will release parasitic wasps into that area.
Note that the wasps are not expected to stop the demise of my ash trees. My understanding is that the introduction of the wasps is part of a long-game biocontrol strategy that may, perhaps decades from now, yield benefits. It is an entomological shot in the dark, as it were.
For me, helping with this experiment is far better than the two alternatives available:
- Doing nothing but watch the ashes decline as the woodpeckers feast on their dying remains full of EAB larvae, leaving behind a floodplain almost fully devoid of its canopy tree cover.
- Having an arborist inject systemic poisons into the trees. Besides the exorbitant expense (37 60-70-foot tall ash trees), the poisons kill any insect that takes a bite out of treated trees. In his classic book, Bringing Nature Home, Douglas Tallamy notes the number of different insect species that rely on native trees for food. For ash species, his number is 150; that’s 150 different insect species that rely on ash trees as a food source. So if you poison your ash trees to prevent EAB invasion, you will also potentially poison at least 150 native species of insects that rely on ash trees. Further, those now-dead insects — mostly caterpillars — would have fed myriad species of nesting songbirds, which also will likely now die from starvation.
You cannot break one link in the chain of life without affecting every other link. I pray every day that humanity figures this out — and acts on that knowledge — before so many links are broken that the chain cannot be mended.
This past weekend, I walked the floodplain portion of my yard to count the number of Green Ash (Fraxinus pennsylvanica) trees growing on it. Thirty-seven trees – 17 females, 20 males – most between 50 to 70 feet tall are the dominant canopy species in this part of our property, about an acre and a half. My adjacent neighbors’ properties also include floodplain areas that are dominated by Green Ash trees.
I was devastated when I realized how completely Green Ashes dominate the canopy layer of the healthy wetland that I live beside, because in less than ten years – more likely less than five, it is a near certainty that they will all be dead – felled by a tiny green insect from Asia that no one has been able to stop: the Emerald Ash Borer.
The insect has already killed “tens of millions of ash trees in southeastern Michigan alone, with tens of millions more lost in Arkansas, Colorado, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Massachusetts, Maryland, Minnesota, Missouri, New Hampshire, New Jersey, New York, North Carolina. Ohio, Ontario, Pennsylvania, Tennessee, Quebec, Virginia, West Virginia, and Wisconsin”. Here’s a link to a current map of infected states that is maintained by the Emerald Ash Borer Clearinghouse (Click on the down arrow to move through time to 2015 and watch how many states become infected). The insect is expected to continue spreading until it has killed every ash tree species in North America.
Southeastern US Ash Species
In the southeastern piedmont region of the US where I live, four species of ash are native. Three are wetland species: Green Ash (Fraxinus pennsylvanica), Carolina Ash (F. caroliniana), and Pumpkin Ash (F. profunda). As is evident on my floodplain, these three are important species in wetlands, and when they are felled by the Emerald Ash Borer, the transformation such areas undergo will be profound. White Ash (F. americana) prefers deep, well-drained soils. Its wood has been used for centuries to make fine furniture, baseball bats, and any other wooden item that needs to be strong and lasting. It has been used extensively as a landscape tree.
Animals that rely on ash trees
Humans aren’t the only living creatures who have relied on ash trees for centuries. According to Dr. Douglas W. Tallamy in his book Bringing Nature Home, ash trees support at least 150 species of moths and butterflies – more than hazelnut, walnut, beech, or chestnut. Moths whose caterpillars rely on ash trees include the Promethea Moth, Apple Sphinx Moth, Fawn Sphinx Moth, Great Ash Sphinx, and Banded Tussock Moth. Butterflies whose caterpillars rely on it include Eastern Tiger Swallowtail, Hickory Hairstreak, Mourning Cloak, Red-spotted Purple, Giant Sulphur, and Orange Sulphur.
White ash is an important source of browse and cover for deer. Its seeds are consumed by wood ducks, northern bobwhites, purple finches, pine grosbeaks, fox squirrels, mice, and many other birds and small mammals. The bark of young trees is occasionally eaten by beavers, porcupines, and rabbits. Because of its tendency to form trunk cavities if its top is broken, mature white ashes are highly valued as nesting sites by cavity nesters such as red-headed and pileated woodpeckers, and then secondary nesters such as wood ducks, owls, nuthatches, and gray squirrels.
The same species also utilize green ashes, and game birds such as wood ducks, grouse, northern bobwhites, and wild turkeys use green ash habitats heavily. Green ash woodlands often shelter the highest numbers of bark-foraging and ground-nesting bird species.
What will all these creatures do for food and shelter when every ash tree in North America is dead? No one can predict the future with certainty, but we can look at what has happened in southeastern Michigan, where this has already happened. Massive gaps in forest cover have favored the invasion of non-native invasive plant species. Japanese honeysuckle, for example, is starting to look like kudzu looks in the Southeast. Soil chemistries are changing, as are water cycling patterns, making it more difficult for remaining native species to maintain themselves. All the dead trees initially favored cavity-nesting birds. So the first few years after the ashes died, woodpeckers and other cavity nesters were more abundant. But the profound disruption in the ash-dominant ecosystems soon led to drastic reductions in the insect species the cavity nesters feed on. No insects means no birds. It’s Rachel Carson’s Silent Spring all over again – only this time the culprit is not DDT, but a non-native invasive insect that cannot be stopped.
What is being done?
Ash species in China – the home of the Emerald Ash Borer – appear to be resistant to this insect. Scientists are trying to figure out how to incorporate that genetic resistance into North American ash species. To that end, they are frantically saving as much ash seed as they can, in the hopes that, someday, they can re-introduce the species with genetic modifications that incorporate Asian resistance to Emerald Ash Borer.
That’s the dream. They aren’t there yet. And no one knows how long all the animals that need ash trees can survive without them. No one knows how ecosystems in which ash trees have been essential components for thousands upon thousands of years will handle such a massive disruption – the extinction of a key ecosystem component.
What can we do?
In the face of the inevitable destruction of all our ash trees, what should we do? Information is always our ally, so stay current on developments regarding the Emerald Ash Borer and any potentially resistant North American ash species. At the end of this post, you’ll find a list of links to get you started.
What am I doing?
As for my Green ash-dominated 1.5-acre floodplain, I’m going to start planting other tree species that I know are adapted to similar growing conditions, starting with the species that are already there, and adding more of some additional species that I have already added that appear to be doing well.
But note, this is a total Hail Mary on my part. The trees I’ll be adding will be young. I’ll be long gone before they can attain canopy height. Thirty-seven canopy-sized (50-70-feet tall) ash trees are way too many trees for me to remove as they die. This means dead ash trees will be dropping pieces of themselves all over the place, most likely including on top of other species growing beneath them.
Additionally, I can’t predict what changes in soil chemistry and water and nutrient cycling will occur. My new additions may not be able to handle these changes.
And the pressure from invasive exotic plant species is already enormous on my property. I spend more time and money on their removal than any other landscaping aspect by far. I may not have the resources to prevent invasive plant species from outcompeting remaining species and my new additions.
But the alternative is to do nothing, to throw up my hands and walk away, and I can’t do that. The green world is what keeps me going – physically, emotionally, and spiritually. I will fight for its survival until I can fight no longer.
You suburban and urban gardeners with no ash trees on your properties may think you’ve dodged a bullet this time, but in fact, you only perhaps have a bit more time to prepare for other battles before us. Already in areas where ash trees are gone, another tree in the same plant family is being attacked: White Fringtree (Chionanthus virginicus).
A new gardening paradigm may be our best hope
Your best weapon will be vibrantly healthy home ecosystems. That is why my proposal for 21st-century gardens across the United States is so critical. Every patch of green will be essential to the survival of native animals and plants. Sterile, chemically controlled fescue lawns won’t help them. Healthy, vibrant, beautiful native landscapes might just save them.
The Emerald Ash Borer is now in the county adjacent to mine. It won’t be long before it finds my beautiful ash-shaded wetland. If you live in the southeastern piedmont in areas with ash trees, I encourage you to take your children, your grandchildren – or any child for that matter – to visit healthy ash trees now. Go appreciate the beauty of their dangling seeds, their compound opposite leaves, their gray furrowed trunks. Lock these images into your memories now, for soon they will be all you have left.
- For North Carolinians living in Orange and Durham counties, on Aug. 20 at 9:00 a.m., the NC Department of Agriculture will hold a public information system on the Emerald Ash Borer quarantine at the Whitted Building in Hillsborough.
- NC Forest Service Web site on the Emerald Ash Borer
- National Emerald Ash Borer Clearinghouse
- Predatory wasps as control for Emerald Ash Borer
- Good photos and information on White Ash in North Carolina
- NC Forest Service list of invasive insects to watch for
- Other dangerous invaders fast approaching:
One minute, summer sun kisses green leaves, flowers abound, birds sing. Then you blink, and color happens.
For some plants, color comes in patches at first.
Or this ornamental spirea:
Fall fruits droop heavy on branches, then tumble to earth.
The native Black Walnut (Juglans nigra) has finally dropped all its nuts. For a few weeks, walking beneath it required a hard hat.
This past Tuesday, a strong cold front approached. Thick clouds darkened the sky, winds blew in gusts, twirling falling leaves into eddies of gold and red. Later that day, the rains came — almost two inches. The trees that always abandon their leaves first took the winds, rain, and ensuing cold air as their cue.
The first native trees to bare their branches for winter in my yard are always the Ashes. Ash trees dominate the active portion of our floodplain — about an acre or so. I think they’re probably Green Ashes (Fraxinus pennsylvanica), but local experts tell me this species often interbreeds with other native Ash species, so I’m not certain.
Their fall color is subtle, but they do cast a distinctive yellow-green glow over the canopy just before they discard their summer clothes.
Ashes are not the first trees most folks notice when walking through their native moist habitats, but they are key components. Their numerous seeds are devoured by many bird species, including Wood Ducks. The larvae of several of our more colorful southeastern US butterflies eat Ash leaves, including the Eastern Tiger Swallowtail, Orange Sulfur, and one of my favorites, Mourning Cloak. This beauty has dark wings edged in deep gold; I count myself lucky when I spot one or two floating through my floodplain, usually on warm late-winter days, when the over-wintered adults begin seeking mates.
Ashes are easy to identify. They have compound leaves. Botanists define a compound leaf as consisting of a set of leaflets. For example, Poison Ivy has a compound leaf. Those “leaves of three” we all look for actually comprise one leaf. Look for a longer leaf stem (a petiole) that attaches the multi-leaflet leaf to a branch.
A casual observer might confuse the compound leaves of Ash trees with those of another Piedmont forest regular — Hickory, but a closer look is all you need to tell the difference. Ash leaves are attached to branches directly opposite each other. This opposite-leaved arrangement is less common in our native trees and shrubs. A single-leaved tree with opposite leaves that we all know is our native Dogwood. Hickory leaves alternate on the branch, plus most have fewer leaflets per leaf than Ash leaves.
After the rains blasted through, the next day, most of the Ashes on my floodplain were bare. In the blink of an eye, their subtle color was gone.
This year as the Ashes performed their vanishing act, I got a knot in my stomach. I couldn’t help but wonder if this will be the last year I am able to enjoy their subtle drama. Why?
The Emerald Ash Borer, a non-native, devastating tiny insect, has a confirmed presence in a few NC Piedmont counties just north of mine. This insect has already killed every native Ash tree in many of our northern states. Every single one. They do it in one year. Experts have no idea how to stop them. Here’s the latest information from the NC Forest Service on this Ash-killing bug. Follow the links on that site to learn more.
A key take-away message about preventing the spread of Emerald Ash Borer and several other devastating non-native insects is about firewood. It is critical that any firewood you buy be from local, uninfected trees. Unfortunately, the firewood industry is not closely regulated. Recently dead trees look like a prime source of money to firewood purveyors. More than half the states in the US, including all of the Southeast, have imposed some firewood movement restrictions. Click on your state on this map to see what restrictions apply for you.
Ignorance is our greatest enemy in the fight to save our Ash trees. If you buy firewood, I urge you to learn what counties in your state are still considered safe sources of uncontaminated firewood. Be wary of pre-packaged firewood sitting outside grocery and hardware stores. Odds are it was shipped in from somewhere else. Ask the store manager where the firewood came from, and if he or she doesn’t know, tell them why you won’t be buying from them.
In my area during every impending cold spell, I’ll see folks selling pick-up trucks full of firewood in parking lots. Firewood sales are a supplemental source of income for most of these folks; many of them probably have no knowledge of the restrictions on where they should be collecting their firewood. In North Carolina, no one should be buying or selling firewood from Granville, Vance, or Person counties outside the boundaries of these counties. They are quarantined due to the confirmed presence of the Emerald Ash Borer. Here are the areas in the US with currently imposed Emerald Ash Borer quarantines.
Unless the experts devise a way to kill this insect in the next few months, it is just a matter of a year, perhaps two, before every Ash tree on my property — about a dozen 75-foot trees — will be dead. Their absence in the landscape will be visible to even the most casual observer. What will be less obvious is the disruption in the Piedmont ecosystem where these trees occur. Birds and insects that evolved to rely on Ash trees as a food source will go hungry. If they cannot adapt to other food sources, they will die trying to find Ash trees elsewhere.
No one knows how many components of an ecosystem can disappear before the viability of the entire ecosystem is destroyed, so that the remaining components die. Think of it as an ecosystem-scale game of Jenga. Sooner or later, the wrong piece is removed, and the entire structure fails.
In the blink of an eye, our native Ashes may disappear. How many more blinks before our native forests are gone too?