Assessing the off-target movement of tebufenozide in forested ecosystems: implications for vernal pond ecosystems

The widespread use of pesticides has significantly contributed to managing pest populations in both agricultural and forest ecosystems, yet concerns about their unintended impacts on non-target habitats continue to grow. Tebufenozide, a pesticide commonly used to control forest defoliator pests, including spongy moth (Lymantria dispar dispar), is known for its selective action on Lepidopteran larvae. Despite its targeted mode of action, the potential transport and fate of tebufenozide into sensitive forested aquatic habitats, such as vernal ponds, is not well understood. This study examines the spatial distribution of tebufenozide in 41 vernal ponds located within three state forests in central Pennsylvania (Bald Eagle, Rothrock, and Tuscarora) by analyzing sediment and water samples collected within and outside designated spray blocks. Tebufenozide was detected in 39 water samples and 40 sediment samples, including 27 unsprayed water and sediment samples, indicating possible pesticide drift or runoff into non-target areas. We used a Mann-Whitney U test to reveal significantly higher concentrations of tebufenozide in ponds within spray blocks for both sediment (W = 241.5, p = 0.0161) and water (W = 316.5, p = 2.769e-06). Tebufenozide concentrations were higher in ponds closer to spray zones, suggesting proximity influences pesticide levels, though no clear directional dispersal patterns emerged. These findings underscore the vulnerability of vernal ponds, essential breeding habitats for amphibians and other organisms, to pesticide contamination. Enhanced management strategies, such as wider buffer zones and alternative pest control measures, may be necessary to safeguard these critical ecosystems.