By: Stanton Gill, Regional Specialist, Central Maryland Research and Education Center, University of Maryland Cooperative Extension and professor with Montgomery College, Landscape Technology 301-596-9413

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.

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.

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.

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.

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.

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.

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.

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:

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%

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

Imidacloprid applied with Kioritz 33%

Imidacloprid applied with high pressure 86%

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.

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.”