Effects of Bacillus thuringiensis subsp. kurstaki application on non-target nocturnal macromoth biodiversity in the eastern boreal forest, Canada

Young, Jodi Olivia (2023) Effects of Bacillus thuringiensis subsp. kurstaki application on non-target nocturnal macromoth biodiversity in the eastern boreal forest, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

Lepidoptera, including butterflies and moths, play vital roles as herbivores, pollinators, and food sources, but also include species considered forest pests. The impact of Bacillus thuringiensis subs. kurstaki (Btk), a widely used bio-insecticide for controlling forest pests like the spruce budworm, on non-target lepidoptera in Canada remains uncertain. To address this, I established a replicated field study to evaluate the effects of Btk on non-target nocturnal macromoth communities in the eastern boreal forest of western Newfoundland, Canada. Over two years, I sampled moths across four groups: north treatment, north control, south treatment, and south control. My analysis focused on species diversity, abundance, and composition. Results showed no significant differences in total abundance or species composition between treatment and control groups. In 2022, control sites had significantly higher Hill numbers for Shannon and Simpson diversity compared to treatment sites. In 2021, differences in Hill numbers were only observed between north controls and treatments. These findings indicate that after multiple years of treatment, there can be shifts in the relative abundance of certain species, but without significant changes in species richness, total abundance, or composition between control and treatment groups. These results suggest that Btk can lead to stand-level shifts in relative abundance but does not substantially alter community structure during the early stages of treatment. The responses of species are idiosyncratic, likely influenced by differences in phenology and voltinism. Monitoring the impacts of Btk on non-target lepidoptera is crucial to effectively manage forest pests while minimizing unintended consequences for non-target species.

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