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Asian beetle threatens Farber’s urban forest

Posted on Monday, April 12, 2021 at 1:39 pm

By Barry Dalton
bdalton@vandalialeader.com

Emerald Ash Borer. Pennsylvania Department of Conservation and Natural Resources.

In December 2020, privately contracted arborists explored the parks and streets of Farber as they inventoried its public trees. What they found could potentially destroy 65 percent of Farber’s urban forest within six years.

The Davey Resource Group (DRG) of Kent, Ohio, was commissioned by the City of Farber as part of a grant from the Missouri Department of Conservation (MDC) through its Tree Resource Improvement and Maintenance (TRIM) cost-share program. The arborists visually assessed trees in the public right-of-way as well as the parks, public library, community center and fire station.

The goal was to determine what steps the city should take to ensure that it maintains a healthy green canopy for years to come. Trees not only help remove pollutants from the air, reduce stormwater runoff and help with energy consumption by providing summer shade, but they also have significant social, leisure and psychological benefits.

In its January 2021 report, The Davy Resource Group found that Farber’s tree population is in fair condition (68%) with most also being mature (60%) with a diameter of greater than 24 inches. Due to the aging tree population, though, the report recommended that 70 percent of the trees in the parks and rights-of-way be pruned and 27% be removed.

More significantly, though, the report was based on what arborists call the “10-20-30” rule for tree diversity in an urban forest. In the same way that you should diversify your financial portfolio to protect it from market changes in a particular sector, it’s also recommended that a town’s tree population be diverse as well.

Specifically, the “10-20-30” rule means that not more than 10 percent of any given urban forest should be just one species of tree; no more than 20 percent should be of the same scientific “genera;” and not more than 30 percent should be of the same “family.”

Unfortunately, the arborists determined that the most prevalent species in Farber is the green ash (65%); followed by the sugar maple (9%); the silver maple (4%); the northern catalpa (4%); and the Callery pear (4%).

The green ash obliterates the 10-percent threshold at 65% for species, and the ash genera is well past the recommended 20% threshold at 66%.

Furthermore, the ideal tree distribution would have an abundance of newly planted and young trees, with established, maturing and mature trees present in lower numbers. The city’s distribution is the opposite of the ideal trend. The mature trees make up most of the population while young trees are only 4% of the inventoried tree population.

Emerald Ash Borer

The Emerald Ash Borer (EAB), an invasive insect native to Asia, has been identified in Farber, according to the Davey Resource Group. The lack of tree diversity within Farber’s urban forest, and in particular the overabundance of ash trees, makes it particularly vulnerable to the destructive beetle.

Although it is smaller than a penny, the EAB’s potential damage rivals that of the chestnut blight and Dutch elm disease.

Chestnut blight is a fungus that was introduced in North America around 1900, and by 1940, it had wiped out most of the mature American chestnut population.

Dutch elm disease is a fungus spread by the elm bark beetle. Since its discovery in the United States in 1928, it has killed millions of elms.

EAB is thought to have been introduced into the United States and Canada in the 1990s but was not positively identified in North America until 2002 in Canton, Michigan. It has now been confirmed in 14 states, including Missouri, and has killed at least 50 to 100 million ash trees so far. It threatens another 7.5 billion ash trees throughout North America.

The adult beetle emerges from late May to early August to lay eggs. In about a week, the creamy white larvae hatch and bore into the tree. They tunnel as they feed, creating winding galleries, which cut off the flow of the water and nutrients to the tree.

The entire canopy may die back, or symptoms may be restricted to certain branches. Declining trees may sprout epicormic shoots at the tree base or on branches. Woodpecker injury is often apparent on branches of infested trees, especially in late winter.

Trees typically lose between 30% and 50% of their canopy during the first year of infestation and often die within six years. Safety becomes a concern as limbs and trees become unstable.

Once infected, there is no cure. However there are chemical treatments that will protect uninfected ash trees for at least two years. This gives towns and private residents time to develop action plans for treating and replacing their ash trees.

EAB larvae create tunnels that cut off a tree’s water supply. Tennessee Dept. of Agriculture

Action Plan

With the threat of EAB in Farber, it is crucial that the city have an action plan, the report states. DRG recommends the city consider both treatment and safety-related activities on ash trees. Choosing to do nothing would be economical in the beginning of an infestation, but it would become a severe public safety issue within a few years, states DRG.

Removing and replacing all of the ash trees does not need to happen all at once, the report notes. DRG says it recognizes this may be cost prohibitive for small communities as it would require a lot of upfront cost. After removal, for example, the cost to replace all of Farber’s public ash trees is estimated at $34,000 based on recent planting costs.

So if cost is the primary concern of the community, DRG recommends a combination of removing some trees and treating others to stabilize annual removals, annual budgets and prolong the life of ash trees that are currently in good or fair condition.

Specifically, DRG has identified 19 trees in the “poor” and “dead” condition for removal first because they are more susceptible to infestation and, if not removed, could pose a public safety issue. Furthermore, it recommends that Farber chemically treat 46 trees.

 

Replacing Trees

MDC has developed an extensive list of trees based on size, disease resistance, pest resistance, seed/fruit set and availability, as well as their ability to thrive in the Eastern United States that could be chosen to replace ash trees. The list includes a variety of maples, oaks, magnolias, pines, spruces and other common species.

There are many exotic options, too, such as Chinese chestnut, Prairie Pride, Shademaster, Kentucky coffeetree, Emerald Feathers, Shawnee Brave, Persian parrotia, Macho, Korean mountain ash, eastern redbud, european filbert, Winter King, Japanese snowbell, Emerald Pagoda and more.

 

Private Trees

During the inventory, it was evident to the arborists that there is also an abundance of ash trees located on private property. The number is unknown, but it could be equal or more than the ash trees located on public property. The cost to remove ash trees will be higher on private property but if nothing is done it will pose a threat not only to private property but potentially to public safety.

The MDC recommends that private citizens concerned about EAB should consult a licensed arborist. MDC also discourages homeowners from transporting ash trees as firewood as this is one of the primary means of transmission of EAB from county to county.

More information is available at mdc.mo.gov and typing EAB in the search box.

Farber Train Station. Photo by Barry Dalton