Landscape Assessment Research Paper

Landscape

Gypsy Moth Control and the Diana Fritillary (Speyeria diana): A Carolina Landscape in Conflict

The Gypsy Moth is an exotic pest and invasive species that feeds on the leaves in the middle branches and crowns of tress, and while populations tend to persist at low levels in some areas for quite some time sudden and as yet unexplained population explosions can lead to massive defoliations (Liebhold 2003). The Speyeria diana, commonly known as the Diana fritillary, is a butterfly species that inhabits the northwest counties of South Carolina and certain surrounding areas, with recent evidence suggesting that populations might be more widespread than previously thought; unlike many other fritillary species the Diana fritillary primarily populates wooded and shaded areas (Scholtens n.d.). The overlap of these two species is fraught with complications that threaten the survival of the Diana fritillary.

Environmental Issues

There are several significant environmental issues that need to be considered when addressing the effects of defoliation on Diana fritillary in the region, and in the development of a treatment plan to deal with the Gypsy Moth population. As an invasive and destructive species, the protection of Gypsy Moth populations is not a cause for consideration, but typical methods for controlling Gypsy Moth population growth and spread have been shown o have a direct impact on Diana fritillary populations (Scholtens n.d.; Liebhold 2003). Closer examination and careful consideration of these issues is necessary in treatment plan development.

Forested areas in the region occupied by Diana fritillary butterflies are already fairly slim and face numerous threats from direct and indirect human activity as well as other issues (National Park Service n.d.; Sterner n.d.). Maintaining forested areas should be the primary consideration in the development of a treatment plan for restoring and maintaining Diana fritillary populations, however the impact of various reforestation and defoliation prevention methods must also be considered in the development of this plan. Human population centers should also be analyzed and considered in developing a treatment plan, as should wind factors and other influences that can cause a spread of both moth larvae and the bacterial species used to control them (Liebhold 2003; Sholtens n.d.). A full consideration of environmental factors will lead to more effective treatment responses and landscape restoration efforts.

Btk Spraying

The use of Bacillus thuringiensis kurstaki, a naturally occurring bacteria that can be used very effectively as an insecticide, has been used to control the growth and spread of gypsy Moth species for several decades with a fair amount of success (Liebhold 2003; Sholtens n.d). Some research has suggested, however, that Diana fritillary larvae might also be especially susceptible to Bacillus thuringiensis kurstaki infections, and that populations might be decimated by the widespread use of this Gypsy Moth control technique (Scholtens n.d.). The key is in finding a balance between the use of Btk to control Gypsy Moth populations and prevent further defoliation while protecting native species like the Diana fritillary.

As the research has only suggested a susceptibility of the Diana fritillary to Bacillus thuringiensis kurstaki during the larval stage, spraying Btk during other periods of the butterfly's life cycle could potentially avoid the negative impacts of such spraying on Speyeria Diana populations while still exerting control over Gypsy Moth population spread and growth (Scholtens n.d.; Liebhold 2003). Additional assistance in this matter is provided by prevailing weather patterns; current Gypsy Moth populations are still considerably north of known Dian fritillary populations, and with the situation of fronts these southerly populations should not be affected by the use of Btk (Scholtens n.d.). Spraying during the early summer, when the Diana fritillary is in its adult stage and long enough before larvae emerge from eggs in the fall, and concentrating spraying in the areas….....