Neonicotinoid pesticides are applied to seeds and are known to cause lethal and sub-lethal effects in birds and mammals. Neonicotinoid-treated seeds could be available to wildlife through spillage or exposed seeds near or at the soil surface due to incomplete or shallow drilling. We quantified seed spills that may occur during loading or refilling the hopper at a landscape-scale using road-based surveys. We also quantified undrilled seeds in 1-m2 frames on the soil in the center and corner of fields to obtain estimates at the field scale. We broadcast seeds on the soil surface of a tilled field and left them for 0, 1, 2, 4, 8, 16, and 30 days to quantify the decrease of neonicotinoids under field conditions. Lastly, we documented wildlife at neonicotinoid-treated seed spills with trail cameras. We estimated the number of spills during planting to be 3496 (95% CI: 1855–5138) and 2609 (95% CI: 862–4357) for corn, 11,009 (95% CI: 6950–15,067) and 21,105 (95% CI: 6162–36,048) for soybean, and 830 (95% CI: 160–1500) and 791 (95% CI: 0–1781) for wheat in 2016 and 2017, respectively. Exposed seeds were present at the soil surface in 35% of 71 fields. The probability that seeds were present on the soil surface was higher for soybeans (18.8 and 49.4% in the center and corners, respectively) than for corn (1.6 and 2.7%, respectively), and seed densities were also higher (1.04 vs 0.07 seeds/m2, respectively). Neonicotinoids decreased rapidly on seeds on the soil surface but persisted as long as 30 days. Over a dozen species of birds and mammals consumed seeds at simulated spills, with an average time for birds to find spills of 1.3 ± 1.5 days and an average time to consumption of 4.1 ± 3.4 days. Seeds are abundant on the soil surface for wildlife to consume during the spring planting season and should be considered in pesticide risk assessments.
Bibliographical noteFunding Information:
Funding was provided by the Minnesota Environment and Natural Resources Trust Fund and the Minnesota Department of Natural Resources . We are thankful to the landowners that granted access to their crop fields after planting. We thank J. Markl, W. Schuna, R. Markl, N. Trauba, J. Stangel, S. Innvaer, C. Vacek, B. Olson, R. Baden, M. Palm, R. Prachar, E. Hutchins, D. Pietruszewski, J. Williams, and J. Parson for assisting with field planting information. We would like to thank Glacial Ridge National Wildlife Refuge, Talcot Lake Wildlife Management Area, and Roseau River Wildlife Management Area for accommodating technicians during field work. We would like to thank J. Markl, M. Palm, and A. Killian for acquiring seed. T. Fields, A. Mosloff, R. Kreb, and M. Zagorski surveyed for seed spills. R. Wright assisted with DNRSurvey. L. Gilbert provided clerical support. M. Larson provided comments that improved this manuscript.
- Midwestern United States
- Treated seeds
PubMed: MeSH publication types
- Journal Article