Invasive beetles threaten Eastern Shore wetlands

Bob Zimberoff
Posted 3/18/17

Contact Maryland Department of Natural Resources Forest Service if you see ash tree damage

CAMBRIDGE — The Emerald Ash Borer, an invasive beetle that has cropped up in three Eastern Shore …

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Invasive beetles threaten Eastern Shore wetlands


Contact Maryland Department of Natural Resources Forest Service if you see ash tree damage

CAMBRIDGE — The Emerald Ash Borer, an invasive beetle that has cropped up in three Eastern Shore counties, including Dorchester, will kill most of the region’s ash trees and could radically change the ecology of our wetlands, scientists told a workshop on forest health in Cambridge.

Pumpkin ash and green ash dominate many wetlands on the Eastern Shore. These swampy and marshy places and the plants that inhabit them filter sediment from upstream that would otherwise pollute the Chesapeake Bay. They also play a vital role in reducing erosion when storm surges and floods occur, scientists from the Maryland Department of Agriculture, the state’s Department of Natural Resources (MD DNR) and the University of Maryland Extension service said at the gathering Saturday.

Scientists do not know if other plants will eventually compensate for the expected loss of the dominant trees and enable swamps and marshes to perform the same valuable functions they do now.

Individual landowners can save their ash trees by treating them with chemicals if the trees have not lost more than a third of their foliage to the beetles already. But the process, best done in early to mid-spring, can be costly and needs to be repeated every few years, making it impractical for wild ash trees growing in inaccessible, mucky areas.

Originally from Asia and eastern Russia, the half-inch long, bright green-and-purple Emerald Ash Borer appeared in Michigan in 2002. Experts believe it hitched a ride to the United States in solid wood packing material. A year later, it was detected at a plant nursery in Maryland’s Charles County.

By last year, the pest had killed most of the ash trees in western Maryland, according to a draft research paper presented at the meeting sponsored by the MD DNR Forest Service. Then, dead ash trees were found in Easton and St. Michaels, as well as parts of Dorchester and Queen Anne’s counties.

“The impacts of EAB will come sooner than might have been expected,” according to the research paper. “The Emerald Ash Borer will kill all ash trees on the Eastern Shore, many of which are found in sensitive riparian areas,” stated the agenda for the workshop organized by the Extension. Riparian means located along a natural waterway, whether inland or tidal.

Chris Frye, state botanist, MD DNR Heritage, said: “The eventual loss of ash will impact flood plain plant communities.” The tall ash trees and their wide, leafy “crowns” create a shady, moist environment on the forest floor which hosts a unique ecology of plant, animal and insect life. As the trees’ foliage disappears, sunlight will flood in and change conditions on the ground.

He said he feared invasive plants (like Japanese honeysuckle and porcelain berry) would take the native plants’ place. “On a small scale, you can re-plant trees, but on a large scale, it’s just not feasible.”

Along Marshyhope Creek, a 37-mile long tidal creek and tributary of the Nanticoke River that runs through Dorchester and Caroline counties, as well as Delaware’s Kent County, ash trees have suffered “99 percent mortality, although saplings have survived,” Chris Frye added.

The main types of ash growing on the Eastern Shore are pumpkin ash and green ash. “Pumpkin ash occurs on the outer edge of tidal marshes,” while “green ash grows in the back swamps along the Marshyhope.” One in five trees there is an ash.

Watersheds where the green beetle will likely devastate ash tree populations include the Choptank River watershed, near Cambridge, the Chester River watershed, to the north, and the Nanticoke and Pocomoke River watersheds, on the lower Eastern Shore.

Dr. Andy Baldwin, Wetland Ecologist, University of Maryland, said tidal freshwater forested wetlands where both types of ash grow “get a little salinity, but not very much.” Typical of these areas are small hummocks of earth, surrounded by water, where “micro-habitats with different amounts of flooding” occur. In these, live “a great diversity of plants.”

The scientist said he expected “a massive disturbance due to the dominant species going.” He was “trying to start research and looking for funding.”

An example of what could happen on the Eastern Shore occurred in Anne Arundel County’s Patuxent Wetland Park last year. Green ash dominated the tidal swamp until Emerald Ash Borers killed the trees. Since then, so-called understory growth has increased tremendously, due to the influx of sunlight, and the ecology has changed dramatically.

Colleen Kenny, EAB program coordinator, DNR Forest Service, presented less of a doomsday scenario, however, describing “bio-control” as a “long-term strategy.” Scientists here, as well as in Ohio and Michigan, were experimenting with “parasitoid predator wasps,” she said. Also from Asia, the insects destroy the green beetles by injecti ng their eggs through tree bark into EAB larvae or eggs. The wasps are not invasive, however, and do not harm other creatures or plants, she said.

The main sign that an ash tree is infested with Emerald Ash Borers is if the foliage at the top dies, followed by the entire tree.

Woodpeckers tapping can signal that a tree is dying or dead. Infested trees snap easily. If an ash tree is not slated for treatment, it should be cut down and the wood burned without being moved to another site. However, many tree companies will not work on an infested tree.

If a tree has lost less than 30% of its canopy to borers, consider treating it with insecticide – either by drenching the soil or injection into the trunk. Restrictions apply near waterways, however, and some products should be applied only by a licensed technician or arborist.

Scott Daniels, forester, DNR Forest Service, Dorchester County, advised owners of woodland to contact their county’s forester to develop a Forest Stewardship Plan. The plan carries tax benefits and costs a nominal amount: For 5 to 25 acres, about $200, he said. Contact Mr. Daniels at 410-228-1861.

Please report infested trees to the County forester or to:

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