May
2014

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

Download the audio files or subscribe to our podcast.

 

Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

05-22-14

Download the audio of On Six Legs: MP3, WMV
Follow us online at Purdue Agriculture News Columns

There's a New Moth in Town


gypsy moth
Gypsy moths mating

photo credits: John Obermeyer / Purdue Entomology

There's a new moth in town! Could that be the plot of an old western movie starring John Wayne? Or is it the latest episode in a crime-laced TV series? The answer is neither. The answer is that gypsy moths have been found right here in our fair city of West Lafayette, Indiana.

For those who are not familiar with gypsy moths, let me fill you in. Gypsy moths are insects that we humans don't like. We call them pests. That is because caterpillars of these moths feed on the foliage of at least 500 species of plants, including most trees and shrubs. Some of the preferred tree hosts are apple, birch, oak, poplar and willow, all of which are important forest and urban trees of the Eastern United States.

Feeding by gypsy moth caterpillars can entirely defoliate a tree. Such defoliation reduces the beauty of trees in the landscape. It can increase stress on the trees resulting in tree death. So having these caterpillars chowing down on our trees is not a good thing. That is why we call gypsy moths pests.

Why are these tree pests known as gypsy moths? They are called moths because that's what they are in the adult stage. Why the name gypsy is used is not as clear. It most likely has to do with the fact that the larger caterpillars tend to crawl up and down the trunks of trees on which they feed. Such behavior was suggestive of the nomadic lifestyle of the people known as Gypsies.

The scientific name of the insect is Lymantria dispar. Carl Linnaeus assigned the scientific name to the gypsy moth in 1758. He gave it the genus name lymantria that literally means destroyer in Greek. An appropriate name based on the damage caused by the caterpillars. Linnaeus assigned the name dispar for the species. This Latin term, meaning separate, was descriptive of the obvious differences in size and coloration of the male and female moths. The male moth is smaller than the female and is a tan color while the female is white.

gypsy moth feeding
Gypsy moth larva feeds on foliage

Gypsy moths have not always been pests of trees growing in the forests and urban boulevards of the Eastern United States. This insect is what is called an exotic pest. That means the insect species is not native to our shores. In this case, it was originally found in Europe. Unlike many of our exotic pests - think here about insects such as the Japanese beetle, the emerald ash borer and the European corn borer - the gypsy moth was actually deliberately transported to the United States.

Yes, siree Bob, someone intentionally brought the gypsy moth here. And that someone was a French astronomer by the name of Etienne Trouvelot, who was interested in improving the silk industry here in the U.S. He imported a few of the silk-producing gypsy moths to his residence in Medford, Massachusetts, in 1869. Some escaped and the rest, as they say, is history. Since then, these insects have been moving westward on their own at some seven to 13 miles per year. They disperse by crawling as caterpillars, primarily to find a place to pupate. The newly hatched caterpillars also lower themselves on a silken thread that allows them to swing, courtesy of the wind, to adjacent trees. Apparently, in some cases, the little caterpillars can ride the wind for up to a mile.

Occasionally, a gypsy moth population can get established many miles from infested areas. This results when females attach egg masses to firewood or even automobiles or camping trailers. These egg masses might end up being transported almost anywhere. If that location is outside the current distribution area of the gypsy moth, a new infestation might be established. That was probably how the first gypsy moths arrived in West Lafayette, Indiana.

So what will be done about the new pest in town? Well, in this case, the strategy will be to use a pheromone-based, mating-disruption strategy. Here's how it works. Like many moths, the male moth will detect the flightless female because she produces a pheromone. So if enough commercially produced pheromone is released in an area, the males will not be able to locate the females. No mating will occur, and no eggs will be produced. And no caterpillars will hatch. And next year, the gypsy moths will have disappeared. And that's a good thing! 


 

Writer: Tom Turpin
Editor: Olivia Maddox