The emerald ash borer lays larvae between the bark and woody tissue of ash trees which then slowly eat the tree, starving it of nutrients. As adults, these exotic Asian insects bore out leaving a distinct pattern on the infected trees.
Michigan City Urban Forester Frank Seilheimer said several of the trees were on phase two of infestation. This means trees will cease to grow leaves at their tops, but will continue to have full leaves at the center and sprout new shoots towards the bottom, due to the tree's inability to send nutrients to its top.
Seilheimer added that the trees were planted during the 1970's and 80's to replace the elm trees that once lined the corridor and had to be cut down due to Dutch elm disease -- a fungal infection.
Authorities suspect the emerald ash borer came to Michigan City from Detroit after an Asian shipping container entered the country through the Detroit Metro Airport.