Ashes, ashes, they might fall down.
Ash trees, that is. Emerald ash borer (EAB), an invasive Asian pest that has already killed over 30 million ash trees in North America, is spreading in Wisconsin, and has been detected in Janesville, just 28 miles south of Madison.
While neither the insect nor its larvae have been detected in Dane County, Karl van Lith, a member of Madison's EAB task force, says it's likely they're here. The task force has preemptively made four recommendations in an attempt to mitigate the impact of EAB, according the task force's June report (PDF).
EAB are spread mainly through firewood transport via interstate highways. Once infected, ash tree canopies begin to thin from the top down. At a meeting of the Madison's Committee on the Environment Monday evening, city forester Marla Eddy explained that the pests are most harmful at the larvae stage, when they burrow underneath the bark and feed on the tree's nutrients. Eddy noted that at high levels of infestation, ash trees can die within 1-2 years.
The first two recommendations of the task force have to do with removal of trees. Ash trees in "poor condition" are considered to be untreatable if they are damaged by more than 40 percent. The recommendation states some of the removal should take place during infrastructure projects and repairs. If accepted, the recommendations would also allow property owners the option to have healthy trees removed as well.
All removed ash trees would be replaced by other tree species. Eddy explained the city generally tries to plant three different tree species per block to avoid losing 100 percent of canopies in the case of another infestation. But Water Utility Board representative Dan Melton pointed out that ash trees appear to grow "block by block," dominating some streets and non-existent on others.
Other recommendations involve chemical treatments, which would only be implemented once EAB or its larvae are detected in the county. There are currently four chemicals that have been found to successfully protect healthy trees from EAB.
"None of the pesticides are going to eradicate EAB," van Lith told the committee. However, he said they will help slow the damage.
The committee raised concerns about the potential harmful impacts of chemical treatments. In a brief post-meeting interview, committee chairman Steve Fix said his main concern was the effect chemicals could have on surface water, but he said hearing the task force's report put those concerns to rest.
Van Lith said at the meeting that injection is the best way to apply chemical pesticide treatments because it minimizes water contamination. But, the task force report states that the long-term ecological impacts of chemical treatment are unknown.
Madison Parks Forestry sampled 550 ash branches last winter and found no EAB larvae, according to a city news release. The task force plans to continue branch sampling at half-mile intervals, according to the report.
The Committee on the Environment approved the task force's recommendations Monday night. Several other committees still need to approve the recommendations before they can be reviewed by the Common Council.