by William Hengst
As mentioned in the June 5 issue of the Local, ash trees are undergoing a decline due to other pests and diseases besides emerald ash borer (EAB), such as ash yellows. Ash yellows is a microplasm, or virus, transmitted by native leafhopper insects that infect the phloem or the food-conducting tissues of ash trees, shutting them down more gradually than EAB. Its symptoms mirror the early symptoms of EAB, namely declining growth, leaf and branch dieback. Unfortunately there is no treatment for ash yellows. An infected tree may live for many years, however it will become weaker and more likely to get EAB, and eventually will die.
Ash rust and anthracnose
Zach Shechtman, owner of Shechtman Tree Care, in an email communication wrote, “We’ve received many calls this spring from people thinking they have EAB when really their tree is losing leaves due to ash rust and ash anthracnose. Ash rust is a foliar fungal infection, characterized by orange or yellow growths on the leaves and stems. It causes leaf drop and in some cases full defoliation that look serious but usually pass as new leaves grow.
“Anthracnose has been plaguing ash trees over a number of years. Anthracnose, and now ash rust, are the main reasons ash trees look sparse. Repeated early leaf drop or late bud break does take a toll on plant vigor and will leave ash trees more susceptible to EAB.”
According to Peter McFarland, president of McFarland Tree Company, “Ash rust was serious in spring 2013 and worse this spring. Between years of build-up of anthracnose, and more recently ash rust, ash trees are really stressed. Each spring they leaf out for six weeks and then drop their leaves, With no more photosynthesis the trees go dormant for 10 months. This does not forebode well for our ash trees.”
According to Steve Pascavitz, certified arborist at the 55-acre Awbury Arboretum, “a lot of our collection is older trees and some may be reaching the end of their life cycle.” He cites extreme hot and cold climate conditions as a stress on Awbury’s iconic, native tree canopy.
In the past several years, the arboretum has removed a dozen or so of its older ash trees in decline but does not have funds in its budget to remove the rest of them (approximately 30 more). Pascavitz also stated they would like to begin insecticide treatments against EAB but don’t currently have the money.
The Morris Arboretum already has the benefit of knowing where all its ash trees are and they continue to monitor them for signs of decline. “We have begun protecting several of our mature ash trees against EAB with the insecticide Tree-Age,” wrote Anthony Aiello, director of horticulture and curator, in an email.
EAB Management Plans
The Pennsylvania Bureau of Forestry received a federal grant through the state’s Urban Forestry Council to assist 11 communities undertake tree inventories, ash tree assessments and prepare EAB management plans. The communities include Philadelphia, Easton, Lancaster, Reading, Pottstown, West Chester, Pottsville, and several other towns across Pennsylvania. The Bureau of Forestry has prepared guidelines, which other communities can follow to prepare for and deal with EAB. (Google “Emerald Ash Borer Management Plan for Pennsylvania Communities”)
City of Philadelphia
Philadelphia has approximately 125,000 ash trees, the vast majority of which are in the Pennypack and Wissahickon watershed parks and on private residential properties. The city has already prepared a management plan, which can be read at www.phila.gov.
Philadelphia’s plan recommends a proactive approach in which all ash trees located within 100 feet of a trail, road, or structure will be removed for public safety reasons; the plan estimates 7,000 ash trees should be removed due to location or poor health.
The city has awarded a contract to begin this year removing some of these ash trees and other tree species in decline or considered hazardous because of their location. According to Curtis Helm, park manager for the city’s Parks and Recreation Department, the city hopes to begin insecticide treatments next year of a thousand or so ash trees, provided funds are available.
The Wissahickon Environmental Center (formerly Andorra Natural Area) has already benefited from the city’s efforts. “All of our ash trees have been identified with tags, which will facilitate monitoring their condition,” said education director Trish Fries in a recent telephone conversation.
Schuylkill Center for Environmental Education
Melissa Nase, manager of land stewardship at the the Schuylkill Center, said the center has received guidance from the Bureau of Forestry and expects to prepare an EAB management plan in the future. The Bartlett Tree Company has offered to assist in that effort and volunteers probably will help with the inventory. She said the center has seen a lot of ash rust this spring, but as yet no signs of EAB.
The center has a policy of not using insecticides due to their possible effect on beneficial insects, so it remains to be seen what it might do in the future, if and when EAB arrives. Perhaps biological controls will be an option by then.
The Borough of West Chester, working in cooperation with the Bureau of Forestry and West Chester University, has already done an inventory of ash trees in its three major parks. Last year, half of the ash in Hoops Park, which has the most ash trees, were treated with an insecticide.
“We will treat the remaining ash in 2014 and continue treatment every two years,” said Denise Dunn-Kesterson, borough forester, in a telephone interview. “We also will treat our healthiest street trees.”
Longwood Gardens has a fair number of ash trees and has identified 36 in the gardens, which it plans to protect, According to land steward Tom Brightman, “We have treated some of those trees with trunk injections or soil drenches, and are monitoring the ash in our natural areas beyond the gardens. We also have a replacement plan in place. Likely trees to plant, include black gum, sweet gum, hickories, red maple, and oaks.”
Valley Forge National Historic Park began to document its “landscape-significant” ash trees this past winter, and also has mapped those which could become a hazard after EAB has killed them. According to Amy Ruhe, biologist at the park, “the survey identified high-priority trees that we will want to protect or remove. We also identified large stands of ash where significant tree loss will require we replant, if future funds are available.”
With ash trees in decline and EAB beginning to close in around Philadelphia – this spring the beetle was detected in Berks County and in New Jersey (Bridgewater Township, Somerset County) – local arborists remain proactive.
“We have already treated approximately a hundred specimen ash trees with soil applications and trunk injections,” said Zach Shechtman. “Effective treatment before the infestation gets established is going to be the least expensive and most effective. Ash trees should be monitored as EAB gets closer.”
Ken LeRoy, veteran arborist with J. B. Ward & Company, is particularly on point: “Because we are seeing more and more signs of ash yellows and, now this spring, ash rust, the future of ash trees is grim. Nobody is going to grow ash anymore. We are living in a time when ash trees are going to become extinct. The real issue today is not native-versus-exotic, but rather the loss of diversity in the community tree canopy, and what we are going to do about it.”