Last week, we published an article titled Gypsy moths may win out in Pike, about the possibility that Pike County will opt out of the aerial spraying program in which it has participated for the past few years. We think it may actually be the humans who wind up being the winners if this choice is made—though we may have to give it just a little help.
History suggests that, all things being equal, attempts to work with the natural mechanisms of an ecological system tend to work better than attempts to override them. Defenders of Bacillus thuringiensis (commonly known as Bt), the agent used in the spraying program, note that it is comparatively benign, as it targets only caterpillars that feed on leaves. Unfortunately, that includes caterpillars that grow into butterflies and pollinate plants. With honeybee populations plunging, this is not such a good idea.
It could be argued that gypsy moths are a special case when it comes to the need to spray because they are invasive aliens, introduced to these shores in 1869. Because such introductions are not part of an existing ecological equilibrium, they dont have many natural controls. Indeed, as gypsy moths spread southward from New England, the acceleration in the damage they wrought was at times nothing short of astonishing. In Pennsylvania, defoliated acreage went from 800 acres in 1969, to 10,000 in 1970, to 100,000 in 1971, to just under one million in 1973. That type of geometrical progression is tough to dismiss as a natural cycle that we should just ride out.
Fortunately, it did not continue. The latest peak defoliation in Pennsylvania, which occurred in 2007, was again just under one million acres, suggesting that some stabilization may have been reached. It could be argued that Bt spraying may have been responsible for the stabilization, and it probably did play a role. But there have been other factors at work as well.
Aliens to an ecosystem may have few predators or pathogens to begin with, but that void is filled over time, and thats whats been happening with gypsy moths. One such predator was a deliberate introduction: the Calosoma sycophanta beetle, a large metallic green ground beetle from Europe introduced in 1906. By now, it has become established throughout our area. Then theres a fungus, Entomophaga maimaiga (EM), which has emerged in the past couple of decades as a major pathogen. It was initially imported in 1910 from Japan but did not take hold at that time. But it emerged again in 1989 and 1990 as the primary agent in the collapse of a major gypsy moth infestation in the Northeast.
The control that most commonly brings gypsy moth expansion cycles to an end appears to be the Nucleopolyhedrosis virus (NPV). This one was not an introduction, but developed naturally as an adjunct to the host population.
If Pike County opts out of the spraying program, it will be relying on controls such as these. From the point of view of saving money, sparing the butterflies and avoiding the futility of spraying lands adjacent to untreated forest, this would be an ideal solution. But will it work?
Probably the only way to be sure is to try it. But theres a lot that local households and communities can do to help the natural solution along. And that doesnt mean doing our own personal spraying with harsher chemicals; in fact, one of Pike County Conservation District Director Susan Beechers chief concerns in recommending the opt-out is that the narrowly-targeted BT may be replaced by private spraying of broader-spectrum chemicals that will wreak much more havoc on the ecosystem. What we can do, however, is to provide environments that both strengthen the ability of trees to survive defoliation, and are hospitable to gypsy moth enemies.
Forget about lawn under trees. It competes for nutrients and water. It also replaces the natural wood floor, which is created by having leaves and twigs fall to the ground year after year and rot. The layers of leaf litter and humus provides abundant food for trees and conserves moisture. Let the leaves lie—and just incidentally, save yourself a lot of time and trouble raking.
Such an environment also provides shelter and food for organisms of all kinds that prey on gypsy moths, like mice, shrews and the Calosoma sycophanta beetle. And the EM fungus, whose spores live in soil, has a better chance of survival on a moist woodland floor than a suburban lawn.
Eliminating pesticides would also help. Bt may not kill insects and animals, other than leaf-eating caterpillars, but many lawn and garden chemicals do, and many small birds and animals that are vulnerable also prey on gypsy moths.
All in all, we think Beechers suggestion that the county opt out of the 2010 spraying program is probably a good one. But to give it the best chance to work, we would do well to make our backyards, commercial landscapes and public spaces more hospitable to the organisms that can keep this pest under control.
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Due to state budget cuts, the possibility of closing an elementary school within our district has been looming. During the past two months, on two occasions, over 250 concerned parents and community members in Wurtsboro have attended the Monticello School District Firehouse Budget chats in both Rock Hill and Wurtsboro.