Toxicity of Agrochemicals Among Larval Painted Lady Butterflies (Vanessa cardui).

In the Southern High Plains (SHP) of the United States, beef cattle feed yards and row crop agriculture are predominant sources of agrochemical usage. Beef cattle feed yards use large quantities of veterinary pharmaceuticals to promote cattle growth and health, along with insecticides to control insect pests whereas row crop-based agriculture relies upon herbicides, fungicides, and insecticides to increase yields. Previous studies have documented occurrence of agrochemicals beyond feed yard and row crop agriculture boundaries in uncultivated, marginal areas, raising concern that migratory pollinators and pollinators indigenous to the SHP frequenting these remaining habitat corridors may become exposed to toxic agrochemicals. Larvae of the painted lady butterfly (Vanessa cardui) were used to investigate potential toxicity of agrochemicals used on feed yards and in row crop agriculture among pollinators. Moxidectin, an anti-parasiticide used on beef cattle feed yards, was determined to be extremely toxic to V. cardui larvae, with a lethal dose at which 50% of larvae died (LD₅₀ ) of 2.1 ± 0.1 ng/g. Pyraclostrobin, clothianidin, and permethrin all delayed V. cardui development. However, moxidectin was the only chemical that produced significant toxic effects at environmentally relevant concentrations. These results indicate that agrochemicals originating from feed yards have the potential to adversely impact development of pollinator larvae occurring in the SHP. This article is protected by copyright. All rights reserved.