A battle of insects is being staged nationwide as scientists look for ways to save ash trees On one side is the emerald ash borer, an insect that has killed millions of ash trees, scientists say, and threatens billions more. On the other are three tiny species of wasps that in China have shown they will kill the borer. The experiment is underway in a number of states, including Indiana, Illinois, Maryland, Michigan, Ohio and most recently, last year in Minnesota, West Virginia and Kentucky. More states will try this year, according to Jon Lelito, manager of a U.S. Department of Agriculture lab in Michigan that raises the wasps. Today, officials plan to release the first wasps in Wisconsin at a nature center in Newburg, a community about 30 miles north of Milwaukee, says Andrea Diss-Torrance, a forest entomologist with the Wisconsin Department of Natural Resources. \"How much bang are we going to get for these little guys? We don\'t know right now,\" Diss-Torrance says. \"But when there are no downsides, which there seems to be with this species, it\'s something you should try.\" Lelito says Pennsylvania will start releasing wasps this summer. The emerald ash borer was first discovered in the USA in 2002 in Michigan, according to entomologist Leah Bauer of the USDA Forest Service. Bauer says the borer arrived from China, likely through wood packing material. In 2003, researchers checked ash trees in China for insects that attack the borer, Bauer says. They found three species of wasps and, after ensuring the wasps would not create additional problems, released the first ones in Michigan in 2007. It\'s too early to say whether the wasps will work, and determining results could take years, says Ken Raffa, a professor of entomology with the University of Wisconsin-Madison. \"What we are hoping is it could slow down the spread of the insect, maybe reduce its impact,\" he says. None of the wasps sting, or otherwise pester humans, Raffa said. Bauer said the wasp releases, most effective when temperatures are warm, have so far been isolated, but researchers have been encouraged to see that the wasps have started reproducing in the wild