If you are wondering if clearcuts and herbicides are really necessary in Pennsylvania, you’re not alone. In the past, we’ve written about the devastating effects of a pest known as the spongy moth on our Forest Policy Research. Unfortunately, this is no longer the case. A new study suggests that this insect’s impact on forests is more subtle than we previously thought.
The EPA has approved the use of BtK, an insecticide derived from the Bacillus thuringiensis bacteria. Because the insecticide only impacts leaf-eating caterpillars while they are eating leaves, it’s not a practical option to sample these populations. In order to do this, scientists have developed multiple regression models using data collected in eastern New England from 1911 to 1931. The results of these models indicate that the gypsy moth population system was relatively stable in either phase. Moreover, the analysis reveals that there were a number of natural processes that could terminate the gypsy moth population system.
In the eastern United States, researchers have been working to develop a method for estimating gypsy moth susceptibility. They have produced maps and susceptibility ratings based on the egg mass density of gypsy moths in different forests. The data suggest that the gypsy moth population system is relatively stable in either phase, although a solitary, isolated population of the species is likely to remain in the forest.
The gypsy moth was first introduced near Boston in 1868, and gradually expanded across the U.S. over the next century. While it has not yet reached Pennsylvania, it has spread to southern areas and westward. When gypsy moths are present, the risk of extensive damage increases. This is called susceptibility and damage.
In the east, herbicide applications have lowered the population of the gypsy moth, and fewer larvae have emerged. Increasing the egg mass density of the gypsy moth will reduce the risk of forest damage. Additionally, this method will allow the development of a conifer-dominated stand in a shorter time.
The EPA has approved BtK, an insecticide derived from a bacterium. It is only effective against the leaf-eating caterpillar. It also affects the gypsy moth when it feeds on leaves. In addition, the herbicides have limited effects on the overall population of gypsy moths.