It’s amazing how some of the smallest critters living amongst us can do so much damage. Some of them carry diseases like ticks and mosquitoes, and others kill trees like the gypsy moth, hemlock woolly adelgid, and the emerald ash borer. The tree killing insects are invasive species that have found their way to the US from other countries.
The gypsy moth was brought to Massachusetts from Europe in 1869 by a fellow named E. Leopold Trouvelot. Ole Leopold thought he had found an alternative to the silk worm for silk production and brought a few gypsy moth egg masses back with him. What he didn’t know was the destruction that would follow once those leaf eating caterpillars hatched out all of these years later.
Since then the gypsy moth has spread and established populations in most Northeastern states as well as portions of the Southeast, Midwest, and Canada. One gypsy moth caterpillar can eat one square foot of leaf surface in a 24 hour time period. That’s about the size of a sheet of paper. Each egg mass can contain hundreds of tiny eggs that hatch out as caterpillars in the spring.
Once these caterpillars start feeding it doesn’t take them long to strip the trees of their leaves. When this happens the trees can’t photosynthesize to produce the food and energy they need to survive. Trees can withstand two years of defoliation and then mortality occurs. Oak trees are their preferred species to feed on.
Gypsy moth caterpillars are destructive pests that have caused mortality to hundreds of acres to our forests even here in West Virginia. The majority of the damage is evident by the dead oak trees on the ridgetops of our eastern counties of the state.
Another pest that has left its mark in our West Virginia woods is the hemlock woolly adelgid. The hemlock woolly adelgid is native to Japan and is believed to have been brought to the US via a shipping crate in 1924. Since then, it has established populations from the Smoky Mountains north to southern New England and is having devastating effects on the eastern hemlock stands.
The adelgid attach themselves at the base of the needles and suck the sap from the young twigs which retards or prevents the tree from having new growth. In result the needles turn from their normal dark green color, to a drab grayish green color. Eventually the needles fall off and the defoliation caused by these pests will result in the trees dying within three to six years.
The best way to tell if there is an infestation of hemlock woolly adelgid is to look on the underside of twigs, and egg masses appear as very small cotton balls. The white cottony sacs are present throughout the year, but are more prominent in the early spring. The adelgids are inside the cottony sacs and feed during all seasons, with the greatest damage occurring in the spring when the hemlocks are putting out new growth.
Hemlock woolly adelgid was first detected in West Virginia in 1992 in Grant, Pendleton, Hardy, and Hampshire counties. Since then it has been detected in 48 of our 55 counties of the state. These sap suckers have caused mortality to thousands of hemlocks all across the mountain state including Tucker County.
The most recent invasive insect species to find its way to West Virginia is the emerald ash borer. It was first detected in 2007 in Fayette County and was believed to have been brought in from infested firewood. As result, the West Virginia Department of Agriculture has implemented a do not move firewood policy.
The WVDA encourages folks to not move firewood for long distances, especially when going camping. That’s one of the ways invasive insects can be transported from one place to another. It’s better to collect and burn all firewood from the camping area than to bring your own.
Emerald ash borer is an exotic beetle that is native to Asia and just like the hemlock woolly adelgid it’s believed that it was transported to the US on solid wood packing material via cargo ships or airplanes. It was first discovered in southeastern Michigan near Detroit in 2002. The adult beetles are a purplish metallic color and leave D-shape exit holes when they bore out of the bark. They can fly making them mobile.
The larval stage of the insect lives under the bark and what causes damage and then death to the ash tree. In the larval stage the insect feeds on the inner bark of the ash tree which disrupts the trees ability to transport water and nutrients. Ash trees infested with emerald ash borer will have the D-shape exit holes in the outer bark and they will have S-shape galleries under the bark in the cambium layer.
Emerald ash borer only affects ash trees and death occurs within 2 to 3 years after being infested. The evidence can be seen all across the state by the dead standing ash trees. It’s especially visible all along I-79 for those that travel that route. Unfortunately this pest looks like it will completely wipe out all of our ash trees at the rate it’s moving. Currently 54 out of our 55 counties are infested. Randolph County is the only county it hasn’t been detected in yet.
It’s amazing and scary how quickly just one invasive insect species can cause so much damage and destruction. They’re considered invasive because they aren’t supposed to be here and aren’t native to our habitat. Hopefully there won’t be any more intrusive insect species to find their way into this great state but I’m afraid with the way things are moved around nowadays it’s inevitable.
