How has the gypsy moth affected America?

In the late 19th century, the gypsy moth was mistakenly introduced to North America, and has since become one of the continent's most devastating forest pests. Moth densities reach high levels, over hundreds of square miles, and feed on on the foliage of hundreds of species of plants. Most of what they feed on are oaks and aspen trees. The caterpillars remove most of the foliage from the tree, which can ultimately result in the death of the tree.