Despite the many worrisome announcements that emerald ash borers have been discovered in new Wisconsin counties — 43 of 72 so far — the fact is that most of the state is still EAB-free, according to the state’s Department of Natural Resources.
The devastating insect pest has been discovered in more than 300 of the state’s 1,800-plus towns since first being identified in the state in 2007, but the spread has so far been limited mostly to the southern half of the state. There has been fair success, so far, in keeping the wood-boring insects out of the state’s northern forests, except for small pockets in Douglas, Sawyer and Oneida counties.
The greatest threat is from movement of firewood from quarantined counties to cabin and camping sites in northern forests, according to Linda Williams, DNR forest health specialist. While it is illegal to transport firewood from a quarantined county into a non-quarantined county, it can do just as much damage locally to carry infected firewood into an uninfected area of a quarantined county.
The DNR’s campaign to stop transport of potentially infested firewood is one tool in the department’s arsenal, but another is a collection of tiny insects.
These parasitoids, as they are called, disrupt the egg and larval stages of ash borers so they don’t develop into adults and reproduce. The first experimental release of parasitoids was in 2011, according to Williams. The first release in northeast Wisconsin was 2016 when two larval parasitoids, Tetrastichus planipennisis and Spathius galinae, and an egg parasitoid, Oobius agrili, were released
“These parasitoids are incredibly small, but they find EAB larvae and eggs just fine, helping to reduce the population of EAB,” Williams said. “These parasitoids will not stop EAB, but they are an additional tool we can use to slow the population growth.”
Releases will continue in 2017, Williams said.
The DNR Forestry Division is tracking infestations of emerald ash borers on a map that is updated periodically. The department asks that suspected infestations be reported to the DNR or to the Department of Agriculture, Trade and Consumer Protection, even if it is in a county already quarantined.