MARSHALL TWP, Allegheny County — While the emerald ash borer continues its crusade to kill every green and white ash tree in the eastern U.S., scientists are using 100 years of experience to ensure that “ashes” return in some form.

That was the word from Phil Gruszka, the Pittsburgh Parks Conservancy director of parks management and maintenance, who spoke at a forum at the Marshall Township municipal building Thursday evening.

The forum was part of an environmental partnership between Marshall Township and a fifth-grade class at Marshall Elementary School.

Gruszka told the 50 students, parents and township residents that when a disease or infestation has decimated a specie of tree in the U.S., scientists create a hybrid to replace it.

He cited the chestnut blight 100 years ago and Dutch elm disease in the 1940s and ’50s, after which blight-resistant hybrid versions of the trees were successfully developed.

Gruszka said the emerald ash borer has infested green and white ash trees in 22 of Pennsylvania’s 67 counties, and the state’s entire population of 200 million ash trees will likely become victims of the half-inch-long beetle that made its Pennsylvania debut in Cranberry Township in 2002.

Environmental implications of losing the ash trees in state forestland includes the elimination of 500 billion gallons of water from evaporation from the ash trees.

He said tiny, nonstinging predatory wasps are being released to combat the insect, but significant results will not be seen for a few years.

Sandy Feather of the Penn State Extension shared Gruszka’s grim forecast for the white and green ash tree.

“I wish I were here to talk to you about something a little less heartbreaking than the total destruction of our ash trees,“ Feather told the audience.

She said white and green ash trees can be identified by their compound leaves, which are directly opposite one another on the stem, its canoe paddle-shaped seeds and the rough diamond pattern of the bark of older trees.

Feather explained that the female borers lay their eggs on the bark, and the hatching larvae crawls underneath. The larvae interrupts the tree’s circulatory system, and kills it within two years.

Residents can save ash trees not yet infested by having an arborist inject the tree with selected chemicals or drenching the roots with a chemical mix, Feather said.