Abigail the Green Ash in Alexandria

On July 22, VDOF’s urban & community forestry (U&CF) manager Lara Johnson traveled to Alexandria, Virginia to visit a well-known green ash tree. This ash, located in a courtyard between two apartment buildings, is likely hundreds of years old and is one of largest ash trees in the nation.

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Abigail’s trunks (right and left) each had a circumference of 12’ 9” and 11’ 6” respectively. The tree’s base measured 21’.

Abigail (so named by property managers Mike and Olivia) is the current Virginia State Champion and was once the National Big Tree Champion in the ash category (dethroned only because of qualification adjustments for multi-stemmed trees).

During this visit, Lara was able to remeasure the tree with the assistance of Andrew Benjamin, an arborist with the City of Alexandria. Abigail’s trunks (right and left, as in the photo) each had a circumference of 12’ 9” and 11’ 6” respectively. The tree’s base measured 21’. Lara will report these measurements, along with the tree’s height (78’ 6”) and crown spread, to the Big Tree program.

Protecting Ash
But remeasuring Abigail was not the primary reason for the visit. Lara was there to support the tree’s on-going treatment against emerald ash borer (EAB) – an invasive pest threatening ash trees across the state and beyond. Insecticidal treatment can protect individual trees from the damage and eventual death caused by EAB.

The City of Alexandria had been providing treatment for the tree, but in recent years VDOF was able to offer financial support toward trunk injection treatment of this tree through a grant program developed to protect ash. Using this funding, Lara and Fairfax County staff first treated the Champion tree in 2018. But such funding is limited, and the chemicals and labor required to perform treatment can be costly for landowners, particularly for large trees like this ash.

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Abigail the green ash tree & the 2018 EAB treatment team.

Fortunately, plant health company Arborjet offered to take over treatment of this historic ash tree. Through their “Saving America’s Iconic Trees” program, Arborjet donates treatment against pests and disease for high-profile, iconic trees, like this ash, across the country. Community leaders and homeowners can nominate iconic trees for potential inclusion in the program. These treatments with an Arborjet technician serve as educational opportunities and are open for other professionals to observe.

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A panoramic view of Abigail. To the right in the photo is local arborist Mike Cochran, on-site to observe the application of the injection system and chemical for potential use in his own operation.

Arborjet’s Eastern Technical Manager and International Society of Arboriculture-certified arborist Trent Dicks was on-site to perform the treatment with Lara’s support. Treatment began early in the morning to increase effectiveness. Both Lara and Trent agreed that the high temperatures that Virginia has recently experienced could make treatment challenging because it relies on transpiration – the tree drawing up water (and the chemicals) through the roots into the phloem.

Trent first measured the tree to determine how much chemical was needed for treatment. Then, a series of 34 holes were drilled into the tree’s base as close to the root flare as possible. This presented a challenge, as the tree is below grade and surrounded by a small retaining wall and has very thick “alligator bark” which can be difficult to penetrate.

A plug was placed in each hole, into which a needle would be inserted and pressurized tubes pump insecticide into the tree. The plugs remain in place and a healthy tree readily heals over them.

The duo finished the work quickly as temperatures rose. After less than two hours, treatment and measurements were complete and the small crowd that had formed to observe had dispersed.


Historic Trees
While almost any ash tree in the landscape has potential to be a good candidate, it is the large, historic and rare ash specimens that are often prioritized for on-going treatment because costs can be high.

Did you know?: Green ash trees are a riparian species, and this historic tree is indicative of the relic wetland landscape that once covered northern Virginia.

Abigail is a beloved tree on a “charming, historic property” says property manager Olivia. In the 1940s, the buildings were essentially built around the tree, which serves as a centerpiece in the courtyard and provides shade for residents enjoying time on the patio. “It’s remarkable that this tree survived construction of the buildings. Normally that activity would damage a tree’s root system, but this tree was obviously well-established and the roots were able to recover,” says Lara.

Olivia and Mike explained that they frequently have to clean out the gutters because Abigail’s canopy extends over the roof, and although a bit “high maintenance”, the ash tree is well worth the effort.

Abigail receives other care (such as pruning) from arborists during the year, and although there were historically some signs of EAB impacts (i.e. dead wood), the tree has healed nicely since the 2018 treatment. Thanks to treatment and continued care from certified arborists, there’s hope this tree will stand tall in the neighborhood for many years to come!

Field Notes: The Wind in the Willows, Oaks, Pines …

 VDOF Urban Forest Conservationist Jim McGlone

March 2018 came in like a lion, roaring with sustained winds of 25 to 30 miles an hour.  Predictably, trees fell on power lines causing fires that VDOF personnel worked hard to put out.  Media reports highlighted the mayhem falling trees caused; but there was another big story that didn’t make headlines: while thousands of trees fell, hundreds of millions of trees did not fall.

Wood is strong and flexible; that is why humans have been building with it for millennia. Trees have not only evolved to withstand strong wind, the wind actually makes them stronger.  Just as lifting weights can cause human muscles to grow, swaying in the wind causes wood to grow.  The alternating compression and tension on cells when a tree sways causes those cells to grow more wood.  This results in the taper at the base of a tree.

Most of the trees that fell during the early March 2018 windstorm did so because they were already dead or dying.  Most people can recognize a dead tree, at least during the growing season.  However, they may not recognize a dying tree.  The pictures show a tree that failed during in the windstorm.  Last year it had leaves on it, but when it blew over it revealed that its root system was rotten.

Kidwell Farmhouse fallen tree 2018

Can you see the root rot in the standing tree?  Look closely at the crown and notice the thinning of the leaves on the edges. To a trained eye, this is a sign of root problems.

Upright Kidwell Farmhouse tree

This is why trees, like pets and people, need to see their health care professionals regularly.  Certified arborists are tree health care professionals.

The real story of the March 2-4, 2018 windstorm is not that trees fell and caused mayhem.  It is that strong healthy trees withstood the wind.  And trees grow strong and healthy when they are properly cared for by professionals.  To find a certified arborist near you visit www.goodtreecare.com.

Pretty is as Pretty Does: The Tale of an Emerald Insect Eating its Way Across Virginia

 

“They look so pretty!” That’s what I said the first time I saw an adult emerald ash borer (EAB). But I soon learned from our VDOF Forest Health team that this green insect’s destruction is anything but pretty.

EAB came to the United States from Asia, was first discovered in Northern Virginia in 2008 and is boring its way through ash trees from Michigan to Virginia. “Adult ash borers are metallic green beetles that can be seen flying around the tops of ash trees in late spring and early summer,” VDOF Forest Health Manager Lori Chamberlin said. “These beetles lay eggs on ash bark, and the larvae that hatch tunnel into the tree and feed under the bark. This disrupts the flow of water and nutrients within the tree – effectively choking it to death.”

No ash tree native to Virginia is resistant to EAB, according to Chamberlin. And, unless they are treated before or very early in the infestation, all ash trees that are infested will eventually die.

Hope for Landowners

But there is an arsenal to push these invasive insects back.  “We recommend either a stem injection or a soil drench,” said Chamberlin. “But the time to do this is now, because once an ash tree has lost more than 30 percent of its canopy, it’s too late to save the tree.”

Chamberlin recommends that landowners contact a certified arborist to discuss the treatment options, their costs and the timing of these treatments.

Chemical treatment is effective and most appropriate for high-value landscape trees. Unfortunately, treatment is not normally effective in a forest setting. According to forest survey data, ash makes up approximately two percent of Virginia’s forests. However, it can comprise a significant portion of individual forest stands, especially in riparian and mountainous areas. If you own forestland with a large component of commercially valuable ash, the VDOF recommends discussing your forest management options with a professional forester. Options may range from conducting a silvicultural harvest to doing nothing and leaving the dying/dead trees as wildlife habitat. Check out additional information about professional consulting foresters working in the Commonwealth.

Cutting Edge Push Back

I went out this summer with Lori Chamberlin, VDOF Forest Health Specialist Katlin Mooneyham and University of Virginia Forest Health Intern Kendra Counts  to try out an EAB management method in Cumberland State Forest (check out the video up top).  It was hot; there were mosquitoes and waist-deep poison ivy. But the work this team accomplished will go a long way towards learning how best to fight back against EAB.

As we waved off mosquitoes and navigated the underbrush, Chamberlin and Mooneyham explained that biological control is the most effective effort that we can use in controlling these beetles as they move through forested settings where other control options are not viable. The only other real shot we have at controlling EAB is use of insecticides, but in forests that is difficult because of the amount of ash present and the expense of treatment for that many trees.

“Biological control is a key tool in the integrated pest management toolbox for controlling invasive species,” said Mooneyham. “When we’re faced with a widespread attack, such as we are currently experiencing in Virginia with EAB, we need all the help we can get.”

I like to refer to this summer’s experience as “releasing the hounds,” but we actually released parasitoid wasps. Two releases occurred this summer, one in Whitney State Forest in Warrenton and one in Cumberland State Forest in Cumberland. At Whitney 600 Oobius agrilus (a species that attacks EAB eggs) and 855 Tetrastichus plannipennis (a species that attacks EAB larvae) were released. At Cumberland 400 Oobius agrilus and 403 Tetrastichus plannipennis were released. These wasps pose no threat to humans –– they don’t sting and in fact they are very tiny (really…check them out in the video!).  Tetrastichus plannipennis is only 3-4 mm in size and Oobius agrilus is similarly very small.

And don’t worry; they’re safe (unless you’re an EAB), legal and extensively tested. VDOF received approval to release thIMG_0813ese wasps from USDA APHIS since testing in quarantine showed that they were not a threat to other native insects or animals. This also means that since the wasps are so species-specific for their prey that their population rises and falls along with changes in EAB populations!

 

 

 

 

The VDOF Forest Health staff continues to monitor the establishment of these predators over the next few years at these two sites and hopefully more releases on other state lands will follow. Ultimately, the release of these parasitoids is one of the efforts VDOF is pursuing to protect ash throughout Virginia and gives hope that EAB’s march through our state can be slowed. F

Click here to learn more about EAB or these parasitoids.