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Weather, vegetation, and primary factors of interest and their hypothesized relationships to chemical deposition. Each set of covariates constitute steps in the hierarchical modeling process used to assess insecticide deposition on passive sampling devices (PSDs) and arthropods in Minnesota's farmland region. Height was included in models of insecticide deposition on PSDs but not in models of deposition on arthropods.
Citations
... The presence of insecticide residues could cause birds to avoid contaminated arthropod food items, potentially reducing their food intake and leading to other detrimental effects. Reductions of arthropod food items available following insecticide applications is another important effect to consider, and this has been evaluated in grasslands in Minnesota in a companion study (Chapter 2 of Goebel, 2021). However, Poisson et al. (2021) found that 46% of food boluses brought by adult tree swallows (Tachycineta bicolor) to their nestlings contained at least one pesticide, suggesting that contaminated arthropods are still available to and consumed by birds in the wild. ...
Insecticides are widely used in the Midwestern USA to combat soybean aphids (Aphis glycines), a globally important crop pest. Broad-spectrum foliar insecticides such as chlorpyrifos, lambda-cyhalothrin, and bifenthrin (hereafter, “target insecticides”) are toxic to wildlife in laboratory settings; however, little information exists regarding drift and deposition of these insecticides in fragmented tallgrass prairie grasslands such as those in Minnesota, USA. To address this information gap, target insecticide spray drift and deposition were measured on passive samplers and arthropods in grasslands adjacent to crop fields in Minnesota. Samples were collected at focal soybean field sites immediately following target insecticide application and at reference corn field sites without target insecticide application. Target insecticides were detected 400 m into grasslands at both focal and reference sites. Residues of chlorpyrifos, an insecticide especially toxic to pollinators and birds, were measured above the contact lethal dose (LD50) for honey bees (Apis mellifera) up to 25 m from field edges in adjacent grasslands. Chlorpyrifos residues on arthropods were below the acute oral LD50 for several common farmland bird species but were above the level shown to impair migratory orientation in white-crowed sparrows (Zonotrichia leucophrys). Deposition of target insecticides on passive samplers was inversely associated with distance from field edge and percent canopy cover of vegetation of grassland vegetation, and positively associated with samplers placed at mid-canopy compared to ground level. Percent canopy cover of grassland vegetation had an inverse association with deposition. Target insecticide deposition on arthropods had an inverse relationship with vertical vegetation density and was positively associated with maximum height of vegetation. Tallgrass prairie with cover ≥25 m from row crop edges may provide wildlife habitat with lower exposure to foliar application insecticides. Prairie management regimes that increase percent canopy cover and density of vegetation may also reduce exposure of wildlife to these insecticides.
