Back in 2003 we had the big shake up with introduction of the
destructive emerald ash borer, which was accidentally brought into
Maryland. The Maryland Department of Agriculture took aggressive action,
destroying the infested trees and any ash tree within a ½ mile radius.
They placed out sentinel trees in the area and examined them. They
declared in 2005 that it appeared Maryland was emerald ash borer free.
In 2006 they found ash trees near the original infestation site in a
wooded area that had an infestation of emerald ash borer. One 10”
caliber tree had 17 galleries and 12 larvae present in the galleries.
There were no emergence holes in this tree. MDA representative made an
official press release statement at 11:00 a.m. on Tuesday, August 22nd.
The Maryland Department of Agriculture (MDA) issued a Quarantine Order
(#06-01) that prohibits anyone from moving ash trees or any hardwood
firewood into or out of Prince George’s county until further notice.
Over the next two months the Department of Natural Resources and MDA
will survey the area south of Rt. 4 to locate all ash trees.
In the mid-west the emerald ash borer has changed the landscape and
forest dramatically. The survival of Ash trees in
landscapes and as a forest tree in the mid-west is being severely
challenged. New invasive pest species and native pest are making it a
more demanding task to keep ash trees healthy and thriving in urban
settings. Don’t get me wrong, green and white ash continue to be popular
and be installed in commercial and residential landscapes from the
mid-west and up and down the east coast. Hopefully ash species will
continue to be very valuable in landscapes but it just may take
attention to detail to keep them healthy. MDA and The University of
Maryland Cooperative Extension need your help in keeping this problem
from spreading in the state by reporting in any suspicious small
d-shaped holes on the trunk and rapid dieback on the tree.
Ashes have been a big seller for nursery managers for the last 25
years. In Dirr's book on woody plants he listed Green ash as "a
worthwhile tree for difficult situations." Dirr also calls it the
“everyman’s tree” (this should be updated to “every person’s tree”).
If you desire a large sized shade tree with a 40’ -50’ canopy spread
it is hard to beat the green ash (Fraxinus pennsylvanica.) or
white ash (Fraxinus americana). One of the most popular
glossy leaf, male green ash is the 'Marshall seedless'. It has lost some
popularity in the past couple of years because the overall shape is not
as uniform as some would like it. Many nursery managers are now growing
the cultivar ‘Patmore’, which is a hardier male selection with upright
branches and more uniform outline. The summer foliage color is dark
green and the fall color is a great golden yellow. In white ash the
cultivar ‘Autumn Purple’ has been popular for years.
Sales of liners ash for nurseries has dropped off tremendously on a
national basis since emerald ash borer has been found in the Michigan,
Ontario, Ohio, and Maryland. Maryland nursery managers are still
planting green and white ash but most have reduced the numbers being
planted each year. This may be the nail in the coffin of the green and
white ash market.
New and Exotic Pests.
Maryland has experienced a plethora of exotic pests over the years
but none have the potential for destruction as the tiny green colored
beetle called the emerald ash borer, Agrilus planipenis. This
beetle can devastate ash trees in Maryland in as short a time period as
one season.
If this pest becomes well established in Maryland many landscapes
will be ravaged and the forest dramatically changed forever. This pest
was accidentally introduced into Michigan and discovered in 2001 in the
Detroit/Windsor area. In July of 2002 the beetle was found in Ontario.
The beetle was found in Ohio in 2002 and in Maryland and Northern
Virginia in 2003. The emerald ash borer attacks green, white, black and
purple ash.
How serious is this pest?
Ash trees make up to 1/3 of the forest in the mid-west states such as
Ohio, Michigan and Illinois. Ash are a major component of the forest in
the northeast forest. The Emerald ash borer has the potential to
dramatically change the forest mix if it becomes established. It could
move ash out of favor for use in landscapes. In Maryland White ash is in
the mix but we are dominated by oak and maple forest. Unfortunately, in
the landscape, Green ash has been used heavily over the last 30 years.
It is knocking at our door - again
Officials thought it would be years until we experienced the beetle
in Maryland but it leap-frogged to our state via a nursery tree shipment
from Michigan to a nursery in Prince George’s county. Now it has moved
out of the original infestation site to adjacent wooded areas.
Back in 2003 a Maryland nursery purchased nursery trees that were
shipped from Michigan and the trees were infested with larvae of the
beetle. The plants were left in the nursery during the adult emergence
time in June and the beetles infested additional trees. Some of these
infested trees were moved into Maryland and Northern Virginia
landscapes.
Emerald ash borer infested trees were found in Prince George’s county
in Maryland and Northern Virginia. A trace was placed and the trees sold
out of the nursery have been located in landscape in Prince George’s
county and in Northern Virginia. All of these trees have been destroyed.
By Maryland Department of Agriculture and Virginia Department of
Agriculture. All of the ash trees within a ½ mile radius of the infested
trees from the nursery were cut down and ground up to ½” chips. Work
conducted in Michigan and Ohio found that chipping would, to 1” radius
destroyed all larvae. Choosing a small chip size may be overkill but it
reassures one that the larvae have been destroyed. MDA moved
aggressively attempts to keep this pest from become established in
Maryland. The new federal requirement may be expanding the area that ash
trees must be destroyed.
Sentinel trees were planted around the area where the infestations
were found. Based on work conducted in Michigan, where they found that
ash trees that were physically girdled were highly attractive to emerald
ash borer adults, the MDA planted sentinel trees around the perimeter of
infested sites. These single trees were examined this fall by MDA and
found to be free of Emerald ash borer activity. On revisiting the
original infestation sites some very young ash tree that were not
destroyed on the first go around were quickly destroyed. Hopefully, the
problem, as it appears at this moment, is solved.
Monitoring
The emerald ash borer beetles do not produce any long range
pheromones, so the use of pheromone traps is impossible. The use of
girdled ash trees is probably the best trap method near known
infestations. Keep in mind that even with all of the aggressive
destruction of damaged plants the beetle could slip through the drag
net. We need your help to make sure this pest is stamped out. As
landscape managers we need you to stay alert for problems with Green and
White ash.
Life cycle
Adult beetles start to come out in June and peak in late June and
trail off by mid-July (in Ohio). Adults feed for 10 -14 days before
mating and females oviposit onto trunks, usually on the trunk. They
prefer to lay eggs on larger trees but have been found in trees as small
as ½” diameter. Females lay single eggs, but lay up to 50 eggs over
their life time. Larvae feed in the phloem and scar the xylem. The xylem
is the part of the tree involved with water uptake. The scarring causes
a rapid develop of scar tissue under the bark causing the bark to split.
One of the first symptoms seen is bark splits on the trunk.
Since larvae are just under the bark, wood peckers will be very
active feeding on the infested trees. High wood pecker activity among
ash trees is a good indicator of an infestation. The Downy and Hairy
woodpeckers are the two most commonly found feeding on infested trees in
the mid-west. An infested tree will have round funneled holes from the
woodpecker feeding and d-shaped holes for the emergence of the adult
beetles.
The larvae feed in S-shaped galleries and pack the galleries with
frass. An infestation becomes established when the S-shaped galleries
cross over many times.
Here is what to look for:
1.) Look for D-shaped holes in the trunks of green and white
ash
2.) Rapid dieback of ash tree and formation of witch’s brooms
3.) Shaped galleries under bark that is packed with frass
4.) Presence of small, slender green colored beetle with a brassy
underside
If you see these signs or symptoms contact MDA or an Extension office
and alert them about the site. We cannot emphasize the importance of
destroying this pest rapidly and preventing this pest from becoming
established in Maryland or it will be deadly for Ash trees.
Resistance to Emerald Ash borer
Asian Ash is resistant to emerald ash borer. There is a Manchurian
ash that has been shown to be very resistant. Plant breeders are looking
at these Asian ash for a possible long term solution to developing ash
with resistance to this pest.
Chemicals Control
This is a quarantine pest so all infested trees and trees within a ½
radius will be destroyed so chemical control is not a real option.
Trials in Michigan by David Smitely et.al, evaluated several chemical
control with trunk injection, soil drenching and foliar sprays. Here is
what they found:
Foliage applications in June
Chemical Control
Orthene (single application) 30 %
Tempo 55%
Orthene (2 application day) 57%
Sevin (single application) 69%
Onyx 84%
Onyx (2 applications ) 87%
Tempo (2 applications ) 88%
Sevin (2 applications days) 95%
Trunk Injection
Imicide – Mauget capsule 60-96% at all sites
Pointer (Wedel System) 6 -60%
Bidrin applied in June had variable results
Bidrin trunk injected in mid-July and early September
gave 82 and 77% control
Soil Injection
Imidacloprid applied with Kioritz 33%
Imidacloprid applied with high pressure 86%
What is important to note is that none of the materials or treatments
provided 100% control which means chemical control will not keep emerald
ash borer from becoming established.
Quarantine Area
The quarantine area in Prince George’s County is from the Capitol
Beltway (I-495) and Rte. 4 South. No firewood can be moved in or out of
the quarantine area. Please see map on the next page for more detail.
Summary
Ash, both Green and White ash, are beautiful trees and worth keeping
in the landscape mix but keep in mind that you will need to monitor
these plants closely and keep the Emerald Ash Borer (EAB) and Asian
longhorned beetle (ALB) from before firmly established in the Maryland.
For the native pests, like the banded ash clearwing, timed chemical
applications may be necessary to control the insect borers that can
attack these trees. Meanwhile, those Ginkgo, Tree lilac, Hackberry and
Dogwood trees are looking pretty good. This pest may create new needs
for replacement trees.
The latest information is available at:
www.emeraldashborer.info.
Then click on “eab in Maryland.”