Insect biodiversity is crucial for maintaining resilient ecosystems by supporting essential services, and moths are especially important as herbivores, pollinators, decomposers, and prey for birds, bats, and predatory invertebrates. Despite their ecological significance, large-scale studies assessing the non-target impacts of Bacillus thuringiensis subsp. kurstaki (Btk) on moth communities remain limited, particularly in northern forests where overall lepidopteran diversity is lower.Btk is widely applied in easternCanada to suppress outbreaks of eastern spruce budworm, yet its broader ecological consequences are not fully understood. To address this gap, we conducted a replicated two-year study in the boreal forests of western Newfoundland, Canada, comparing paired Btk-treated and control sites. Our design included two geographic clusters: northern sites, which received treatments in 2020, 2021, and 2022, and southern sites, treated only in 2021 and 2022. Results showed no significant differences in overall abundance or species richness between treated and control sites. In 2021, Hill numbers differed only in northern sites, which may reflect cumulative exposure to multiple years of treatment. In 2022, control sites exhibited higher diversity (Shannon and Simpson metrics) across all locations. Multiple years of Btk exposure also altered community composition and the relative abundance 3 of certain species, highlighting species-specific responses shaped by phenology, voltinism, and sensitivity to Btk.
Young et al. (2026) studied this question.