That’s one option city and state officials are considering as they begin a survey to see how many more of the city’s trees may be infected with the pest. Seven trees in the park and two more on nearby property are known to be affected so far.
City Parks and Forestry Director Doug Gaynor told aldermen Monday the ash borer can travel up to a half mile a year in search of a new food source, so that if all the trees in that radius are removed, it should fail to find food and die off.
However, Mr. Gaynor said, residents should not remove infected trees at this time of year when the adult beetles are active and able to move around.
The time for removal, he said, is between October and April when the beetle is in its larval stage and not on the move.
The city has over 4,000 ash trees on public land. Assuming they are equally distributed, as many as 400 trees might have to be removed to create the barrier to the pest’s spread, and an unknown number of ash trees on private land would have to be destroyed as well.
Mr. Gaynor said, “It’s not wise to think of treating the pest chemically at this point.” Although some treatments are available, they have not proven very effective so far. He said the state will provide advice to local communities on the best treatment techniques once a survey of the scope of the infestation has been completed.
The beetle can also spread by being brought into an area in firewood from infected trees, and Mr. Gaynor said officials believe that is likely how it first arrived in Kane County, the site of the first infestation discovered in Illnois, and then spread to Wilmette and Evanston.
Mr. Gaynor said 30 to 40 arborists from the state and local communities will meet Wednesday for training on how to identify infected trees.
The city’s chief forester, Paul D’Agostino, said that if a quarantine area is established,the foresters will have to figure out how to dispose of destroyed trees within that area — they won’t be able to take firewood, or even wood chips, out of the quarantine zone.