Although Missouri has never had a serious outbreak of gypsy moths or emerald ash borers, it has had close calls. Two cases show how quickly problems can develop and how important alert citizens are to preventing infestations.
In 1992, Arkansas officials discovered a gypsy moth outbreak only 80 miles south of Springfield. An investigation revealed an extremely dangerous and surprisingly advanced situation. Egg masses were spread over an area of 60 to 80 acres.
One windy day could have blown hatching gypsy moth larvae over tens of thousands of acres, making the outbreak extremely difficult -- and expensive -- to contain. If the wind had been out of the south, Missouri could have experienced multiple infestations.
Quick action saved the day, however. A quarantine and the use of effective eradication treatments extinguished the gypsy moth hot spot.
"At that time, Arkansas wasn't trapping as intensively as we do now," says Rob Lawrence, forest entomologist with the Missouri Department of Conservation. "It showed how important it is to stay alert for gypsy moth outbreaks outside the main infestation area in the upper Midwest."
In 1995, a Dent County couple noticed some velvety patches on a golf cart they had brought with them from Delaware. Their previous home area had suffered defoliation by gypsy moths two years in a row, so they knew what the pest could do. They had seen an article with photos of gypsy moth eggs in Missouri Conservationist magazine, so they knew what they had on their hands.
They took a sample to the Conservation Department office in Salem, and the forester there took it to Jefferson City, where it was identified the same day.
This quick response allowed the state officials to spray a 5-acre area with a biological insecticide before the infestation could spread. The product they used contains a protein produced by a native bacteria, Bacillus thuringensis. It is toxic to immature stages of butterflies and moths, which swallow the protein while eating. The bacterial protein has no effect on other insects, plants or animals.
The gypsy moth came to the United States from Europe in the 19th century as part of an experiment with silk worms. Some of those gypsy moths escaped into the wild in Massachusetts in 1869. That started a sort of slow-motion environmental disaster.
Wherever it spreads, the gypsy moth denudes oaks and other trees, destroying forest resources, reducing food supplies for wildlife and causing other harmful effects.
Lawrence said the main gypsy moth-infested area in the northeastern United States has gotten too big for any hope of eradication, and it is only a matter of time until the slow-spreading infestation reaches Missouri. At present, the pest is established in Wisconsin, Illinois, Michigan, Indiana, Ohio, West Virginia, Virginia and most states in the northeastern United States. The southern edge of the infested area expands 5 or 10 miles a year, putting it on pace to reach Missouri in about 25 years. However, every year the state can delay their arrival is worth millions of dollars.
Each gypsy moth caterpillar consumes about 9 square feet of leaf area before changing into an adult. This, coupled with the moth's huge reproductive capacity, often leads to total defoliation of trees. Trees usually recover from one year's defoliation, but repeated loss of leaves often is fatal.
Oak trees are the gypsy moth's favorite food. Because oaks dominate much of Missouri's forest land, experts believe the pest will be especially damaging here. It could change the character of Missouri forests, with accompanying shifts in the supply of natural foods. Deer and turkey, which rely heavily on acorns, could suffer.
Tourism also suffers in areas where trees are denuded by gypsy moths. Bare hillsides are more vulnerable to erosion, and dead timber increases the likelihood of forest fires.