Neonicotinoids are a class of chemical insecticide widely used as pre-planting seed treatments on major agricultural crops such as corn, soybeans, canola, and cereals (e.g., wheat) to control insect agricultural pests. Recently concerns have been raised about the potential immediate and long-term effects of these chemicals on bees and aquatic invertebrates. In addition to toxicity concerns regarding non-target species, these chemicals are relatively water soluble and persistent in soil, raising concern about contamination of surface waters in the vicinity of their use. Widespread occurrence of neonicotinoids in water bodies such as rivers, streams and wetlands has raised questions on what impacts these insecticides may have on non-target ecosystems and organisms.
As a result of these concerns, the approved use of these chemicals in agricultural systems is being re-evaluated in countries such as the United States, Canada, and the United Kingdom.
Neonicotinoids are systemic chemicals, meaning the active ingredient is translocated throughout a growing plant, making all parts of the plant toxic to insects that feed on it. As a result, all parts of a treated plant, including nectar and pollen, receive some dose of insecticide which increases the potential of adverse effects on non-target insects.
Given the emerging evidence for potential impacts of neonicotinoids on many types of animals and insects, the MDC initiated several projects to determine
- if use of neonicotinoid-treated seeds in association with agricultural activities on MDC properties result in concentrations of these insecticides in MDC wetlands at levels that result in ecological impairment, particularly to aquatic invertebrates
- the prevalence of neonicotinoids in the surrounding landscape and water sources and whether these concentrations on MDC properties could have detrimental effects on aquatic invertebrates
- to determine the impact of annual neonicotinoid seed-treatment use on non-target terrestrial insect communities, principally native bees, in Missouri agroecosystems and
- evaluate impacts of neonicotinoids on native bee nesting efforts, development, and reproductive success among solitary bee communities of agroecosystems.
These studies are being carried out to help to direct future management decisions for planted acreages on Department areas. The Department of Conservation plants approximately 67,000 acres of agricultural crop annually on Department areas to provide optimal production of wildlife food and cover with use of accepted best farm management practices, and are managed to provide the best economic return consistent with resource management objectives.
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(Need|s Subscription)An understanding of neonicotinoid sorption and transport in soil is critical for determining and mitigating environmental risk associated with the most widely used class of insecticides. The objective of this study was to evaluate mobility and transport of the neonicotinoid imidacloprid (ICD) in soils collected from cropland, grass vegetative buffer strip (VBS), and riparian VBS soils. Soils were collected at six randomly chosen sites within grids that encompassed all three land uses. Single‐point equilibrium batch sorption experiments were conducted using radio‐labeled (14C) ICD to determine solid–solution partition coefficients (Kd). Column experiments were conducted using soils collected from the three vegetation treatments at one site by packing soil into glass columns. Water flow was characterized by applying Br− as a nonreactive tracer. A single pulse of 14C‐ICD was then applied, and ICD leaching was monitored for up to 45 d. Bromide and ICD breakthrough curves for each column were simulated using CXTFIT and HYDRUS‐1D models. Sorption results indicated that ICD sorbs more strongly to riparian VBS (Kd = 22.6 L kg−1) than crop (Kd = 11.3 L kg−1) soils. Soil organic C was the strongest predictor of ICD sorption (p < 0.0001). The column transport study found mean peak concentrations of ICD at 5.83, 10.84, and 23.8 pore volumes for crop, grass VBS, and riparian VBS soils, respectively. HYDRUS‐1D results indicated that the two‐site, one‐rate linear reversible model best described results of the breakthrough curves, indicating the complexity of ICD sorption and demonstrating its mobility in soil. Greater sorption and longer retention by the grass and riparian VBS soils than the cropland soil suggests that VBS may be a viable means to mitigate ICD loss from agroecosystems, thereby preventing ICD transport into surface water, groundwater, or drinking water resources.
Published on Apr 12, 2018 -Reducing Neonicotinoids in Aquatic Resources: Vegetative Buffer Strips impede imidaclorprid movement in Missouri agroecosystems (PDF, 412 KB)
Neonicotinoids are a class of broad-spectrum systemic insecticides frequently used in agroecosystems to control root and leaf eating pests. The widespread use and environmental persistence of neonicotinoids in the U.S. and globally has resulted in surface water contamination and build-up of neonicotinoids within other environmental sectors, such as soils and wetlands. Deleterious effects of neonicotinoids on non-target insects and wildlife heightens the need to determine practices that reduce potential for these chemicals to reach aquatic ecosystems through subsurface connections and overland surface runoff. An understanding of neonicotinoid sorption (any removal of a compound from solution to a solid phase) and transport in soil is critical for determining and mitigating environmental risks associated with this class of insecticides. We evaluated whether conservation practices, such as vegetated buffer strips (VBS), could reduce neonicotinoid entry into surface waters and aquatic ecosystems. One of the most commonly used neonicotinoids is imidacloprid (ICD) which first entered the United States markets in 1994. This Science Note focuses on differences in the sorption and transport of imidacloprid within soils collected from grass VBS, riparian VBS, and agricultural fields planted to corn/soybean.
Published on Jul 16, 2019 -Science Direct
(Need|s Subscription)Throughout the Midwestern US, many public lands set aside for conservation engage in management activities (e.g., agriculture) that may act as stressors on wild bee populations. Several studies have investigated how wild bees respond to large-scale agriculture production; however, there has been limited assessment of how wild bees may be impacted by agricultural activity on public lands or how local variables may influence bee communities in these same areas. In this study, we assessed the abundance and richness of wild bee floral and nesting guilds at 30 agricultural field margins located on five Conservation Areas in Missouri. Generally, regardless of guild, bee abundance and richness was greater in field margins with more floral diversity and taller vegetation. Bee guilds responded negatively to agricultural production in Conservation Areas with fewer soil- and cavity-nesting bees collected in margins adjacent to annually cropped fields. Although fewer diet specialists were collected, specialist bee abundance and richness was greater in margins near fields that were uncropped (i.e., vegetated, but not row-cropped) during the previous year. Overall, the percentage of trees and shrubs within 800 m of study fields (i.e., “woodland”) was negatively associated with abundance and richness of bees, but specifically, reduced richness of soil-nesters and diet specialists. Our findings indicate agricultural management activities on public lands may lead to decreased abundance and richness of wild bee guilds. If public lands are to be managed for species diversity, including wild bees, maintaining diverse plant communities with taller vegetation (>100 cm) near cultivated fields and/or modifying agricultural production practices on public lands may greatly improve the conservation of local bee communities.
Published on Mar 18, 2019 -Ecological Society of America Journals
(Need|s Subscription)Neonicotinoid insecticides are currently the fastest‐growing and most widely used insecticide class worldwide. Valued for their versatility in application, these insecticides may cause deleterious effects in a range of non‐target (beneficial) arthropods. However, it remains unclear whether strong patterns exist in terms of their major effects, if broad measures of arthropod performance are negatively affected, or whether different functional groups are equally vulnerable. Here, we present a meta‐analysis of 372 observations from 44 field and laboratory studies that describe neonicotinoid effects on 14 arthropod orders across five broad performance measures: abundance, behavior, condition, reproductive success, and survival. Across studies, neonicotinoids negatively affected all performance metrics evaluated; however, magnitude of the effects varied. Arthropod behavior and survival were the most negatively affected and abundance was the least negatively affected. Effects on arthropod functional groups were inconsistent. Pollinator condition, reproductive success, and survival were significantly lower in neonicotinoid treatments compared to untreated controls; whereas, neonicotinoid effects on detritivores were not significant. Although magnitude of arthropod response to neonicotinoids varied among performance measures and functional groups, we documented a consistent negative relationship between exposure to neonicotinoid insecticides in published studies and beneficial arthropod performance.
Published on Mar 30, 2018 -American Chemical Society Publications
(Need|s Subscription)Widespread use of neonicotinoid insecticides in North America has led to frequent detection of neonicotinoids in surface waters. Despite frequent surface water detection, few studies have evaluated underlying sediments for the presence of neonicotinoids. Thus, we sampled water and sediments for neonicotinoids during a one-year period at 40 floodplain wetlands throughout Missouri. Analyzed for six common neonicotinoids, sediment samples consistently (63% of samples) contained neonicotinoids (e.g., imidacloprid and clothianidin) in all sampling periods. Mean sediment and aqueous neonicotinoid concentrations were 1.19 μg kg–1 (range: 0–17.99 μg kg–1) and 0.03 μg L–1 (0–0.97 μg L–1), respectively. We used boosted regression tree analysis to explain sediment neonicotinoid concentrations and ultimately identified six variables that accounted for 31.6% of concentration variability. Efforts to limit sediment neonicotinoid contamination could include reducing agriculture within a wetland below a threshold of 25% area planted. Also, prolonging periods of overlying water >25 cm deep when water temperatures reach/exceed 18 °C could promote conditions favorable for neonicotinoid degradation. Results of this study can be useful in determining potential routes and levels of neonicotinoid exposure experienced by nontarget benthic aquatic invertebrates as well as potential means to mitigate neonicotinoid concentrations in floodplain wetlands.
Environmental Science & Technology 2019 53(18),10591-10600.
Published on Aug 14, 2019 -