DES MOINES, Iowa (KCAU) — A species of bugs known for killing ash trees has made its way to Woodbury County, Iowa State University announced Thursday morning.

Emerald Ash Borer, an inset from Asia, was found in Sioux City, as well as Blencoe and Melvin, by federal authorities. The insect was first detected in Iowa in 2010 and has since slowly encroached into nearly all of Iowa’s 99 counties. The only counties which have not been found to be infected are Plymouth, Emmet and Palo Alto County.

According to ISU, the insect’s larvae typically feed on the inner bark of the trees, this cuts off the tree’s ability to transport water and nutrients which eventually results in the death of the tree. Ash trees are typically killed by EAB within four years of infestation.

While the adult versions of EAB are able to fly and infect other trees, ISU reports that the bugs are usually spread on firewood and other infested materials. As such, one way to stop the spread is by using locally sourced firewood.

Signs of an infestation include canopy thinning, leafy sprouts shooting from the trunk or main branches, bark splitting and woodpecker damage. There are preventative measures that can be taken to protect the tree from infestation. The ideal time for treatment of the infestation is from mid-April to mid-May. Tree service companies can inject insecticides through the summer if there is enough soil moisture.