Neonicotinoids are systemic insecticides with a structure and mode of action similar to nicotine, a naturally occurring plant alkaloid compound toxic to humans. Contact and oral exposures of neonicotinoids target the acetylcholine receptors (nAChR) on the nerve cells within an insect. Neonicotinoids are used on nearly 140 agricultural crops and have many other uses in garden, turf, residential, and animal use. In the United States, five neonicotinoid insecticide active ingredients: acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam are registered for controlling agricultural and urban insect pests. Another neonicotinoid insecticide, thiacloprid registration has been cancelled voluntarily by the registrants and will no longer be available after 2016.
The concern over the use of neonicotinoid insecticides in relation to insect pollinators led the legislature to request that the MDA report on the process and criteria to be used in a review of neonicotinoid use and impact in Minnesota currently and in the future. The Commissioner of Agriculture directed MDA staff on November 5, 2013, to initiate a special review of neonicotinoid insecticides on insect pollinators.
The MDA solicited input from a number of interested stakeholders, including beekeepers, academics, citizens, farmers and their suppliers, and pesticide registrants. In addition, the MDA collaborated with the Department of Natural Resources (DNR), the Minnesota Pollution Control Agency (MPCA), the Minnesota Board of Water and Soil Resources (BWSR) and the University of Minnesota (U of M) to develop a scoping document to be used in conducting the review. The MDA collected and reviewed a significant amount of information and peer-reviewed research related to neonicotinoids and pollinators.
The basic process and criteria that the MDA uses to conduct a variety of pesticide reviews has already been established, and the MDA previously reviewed several neonicotinoid concerns as part of its emerald ash borer insecticide review (including concerns about pollinator exposure). The scoping document identified the underlying criteria to be used in conducting the review. As with previous in-depth special reviews of pesticides, the scope of the neonicotinoid review included an overview of federal and state pesticide programs, roles and responsibilities related to the registration and use of neonicotinoids in Minnesota. The review was carried out using the following six broad criteria:
Neonicotinoids are primarily used for seed treatment. Seed treatment provides efficient and prolonged control of insect pests at low dosages when plants are small and most vulnerable to pests. Farmers also choose neonicotinoids to control piercing and sucking insect pests such as aphids and some difficult-to-control foliage- and root-feeding insects, such as Colorado potato beetles and white grubs. Neonicotinoids show distinct advantages in pest control including efficacy against some boring insects and root-feeding insects, both of which cannot easily be controlled using foliar sprays of non-systemic insecticides.
In Minnesota, there were 510 registered neonicotinoid products in 2015 to control soil or foliar pests. Total sale of neonicotinoid products in Minnesota from 2010 to 2013 was 381,300 pounds. The bulk (>99%) of neonicotinoid products sold from 2010 to 2013 in Minnesota comprised of clothianidin, thiamethoxam, and imidacloprid. In comparison to all chemicals, neonicotinoids accounted for 0.05, 0.12, 0.06, and 0.09% of all chemical products (all chemistries including nonagricultural pesticide products) sold in Minnesota in 2010, 2011, 2012, and 2013, respectively. Because, the state does not have the authority to regulate treated seed, the MDA pesticide sales data does not include pesticide use associated with seeds treated outside of Minnesota’s borders and shipped into the state for planting.
No, toxicity of neonicotinoids depends upon several factors including active ingredient, pollinator species, formulation, application site, plant stage, application time, and environmental conditions.
Neonicotinoid concentrations vary in the plants depending upon several factors including active ingredient, plant species, application method, application timing, prevailing weather etc. Lethality of residues depends upon the pollinator species. Residue concentration of a specific active ingredient may be lethal to one species while sub-lethal to others or it may not show any observable effect on other species.
For an insecticide to become lethal to an organism, the organism must be exposed to a sufficient amount of active ingredient for a sufficient period of time. Bees and other insect pollinators can be exposed to insecticides primarily through contaminated plant parts (pollen and nectar) and through unintended, exposure pathways like insecticide drift and abraded seed dust generated during planting. Pollinators may also be exposed to pesticides via plant guttation droplets, contaminated surface water, or soil. However, the extent to which bees may be exposed via direct contact with guttation, surface water, or soil is considered uncertain.
Abraded dust when released into the air during planting, can contain insecticide concentrations toxic to bees. Bees could be directly ‘powdered’ by insecticides if their flight path went through airborne planter dust or if bees visited vegetation on which planting dust has settled during planting of neonicotinoid treated seed. In addition to amount and type of active ingredient applied on seed, concentration of residues in treated seed planting dust may depend upon the type of planter and seed lubricant used, distance from the application site and abiotic factors such as temperature, relative humidity, and wind.
Currently, the MDA does not have the authority to regulate the sale and use of pesticide treated seeds; they are considered to be “Treated Articles” and not pesticides. Treated articles that meet USEPA’s exemption criteria are not subject to USEPA or MDA pesticide regulations.
Yes, several other insecticide active ingredients can be used as an alternative to neonicotinoids. However, several of the alternatives (specifically older chemistries) may be more toxic to bees, mammals, birds, and aquatic organisms than neonicotinoids.
Laboratory and field studies have produced a wide range of values for soil dissipation half-lives (7 to 6,931 days) of neonicotinoid compounds. In general, half-lives have been reported to be longer for N-nitroguanidines (imidacloprid, thiamethoxam, clothianidin, and dinotefuran) than N-cyanoamidines (acetamiprid and thiacloprid). However, the highest and lowest values may not represent typical half-life values under Minnesota-specific conditions. Neonicotinoid half-life in soils vary with soil type, amount of organic matter, climate, soil pH, moisture, temperature, light intensity, presence or absence of ground cover, etc.
The MDA regularly monitors groundwater and surface water for presence of neonicotinoids in Minnesota waters resources. In groundwater, neonicotinoids insecticides were detected in up to 4.3% of groundwater samples (71 out of total 1,644 samples) in 2014. To date, the detected neonicotinoid insecticide concentrations in groundwater samples have been below the Minnesota Department of Health (MDH) drinking water guidance values of concern. In surface water, neonicotinoids insecticides were detected in up to 4.5% of surface water samples (58 out of total 1,284 samples) in 2014. No neonicotinoids have been found in any lake samples; however, they are being detected in rural and some urban river and stream sites, and in wetland water and sediment samples. The maximum values for neonicotinoid insecticide concentrations in surface water samples have been below EPA’s chronic aquatic life benchmarks for aquatic invertebrates.
Binding affinity of neonicotinoids at the nicotinic receptors in humans is much less than that of insect nicotinic receptors and thus neonicotinoids are considered much less toxic to humans than to insects. Neonicotinoid insecticides were registered by USEPA as “reduced risk” pesticides due to their low mammalian toxicity, thus protecting applicators and farm workers from adverse impacts.
In general, neonicotinoids pose low to moderate risks (acute or chronic) to mammals and birds. Relative toxicity of neonicotinoids to fish and amphibians varies from practically nontoxic to moderately toxic. However, chronic exposure to neonicotinoids at sub-lethal concentrations could be a concern to various taxa.
Executive summary of the review (PDF: 1.10 MB / 10 pages).
The following eight actions are proposed as a result of the special registration review:
Require formal verification of need prior to use of neonicotinoid pesticides, where appropriate.
The impact of proposed actions on increased use of other classes of insecticides which may be more toxic to insect pollinators or other taxa is not known at this time.
In 2015, of the four bee kill incidences in Minnesota, neonicotinoids were observed in two cases. In 2014, six bee kill incidences occurred in Minnesota, of which neonicotinoids were observed in one case.
Minnesota is the first State in the country to carry out a special review of neonicotinoid insecticides. The Oregon Department of Agriculture adopted permanent restrictions for some neonicotinoid insecticides on Tilia spp. (e.g., basswood and linden trees). The State of Maryland passed legislation to become effective January 1, 2018 which makes four neonicotinoid insecticides (clothianidin, dinotefuran, imidacloprid, thiamethoxam) unavailable for purchase or use by the general public. Some states have developed their own pollinator health / protection plans.
The USEPA has opened the dockets for review of all the neonicotinoid pesticides. Below is the USEPA registration review schedule for neonicotinoid insecticides.
One of the major changes USEPA made to neonicotinoid insecticide products approved for outdoor foliar uses is the addition of a “Protection of Pollinators” box. This box visually alerts the user of application restrictions when bees are present by displaying a bee icon, near important information, and accenting key phrases in red “Application Restrictions” and “This product can kill bees and other insect pollinators.” The “Protection of Pollinators” box further describes how foliar applications of these insecticides can result in pollinator exposure, and provides steps for an applicator to follow to reduce non-target impacts. While USEPA has revised labels for foliar neonicotinoid products to clarify pollinator risks and restrict product application during flowering, there are still questions about the ability of these label amendments to reduce impacts on pollinators.
Pollinator decline has also been reported from European countries and Canada. However, honey bee populations are generally not considered to be in decline and insecticide impacts to pollinators are not considered a highly significant issue in Australia.
Health Canada’s Pest Management Regulatory Agency (PMRA), a federal authority for pesticide regulation in Canada, has made some label changes that inform applicators about the potential impacts of neonicotinoid products on bees. In addition, Canada is requiring farmers to use a new corn and soybean seed lubricant called Fluency Agent for planting neonicotinoid treated seeds. At the provincial level, providence of Ontario has implemented new laws effective from July 1, 2015 that require farmers to demonstrate that a pest problem exists before using neonicotinoid treated corn and soybean seeds.
The European Union (EU) member countries have been restricting neonicotinoid use on certain crops since 1999. In 2013, the EU enacted a two year moratorium (December 1, 2013 – December 1, 2015) on application of three neonicotinoid insecticides (imidacloprid, clothianidin, and thiamethoxam) to bee-attractive crops. Updated EU risk evaluations for these chemicals are proposed to be completed by January 2017.
Neonicotinoids are considered to be one of the many factors contributing to the pollinator decline. Banning neonicotinoids might remove one of the possible causes of bee losses. However, a single action might not restore pollinator populations, since other factors such as loss of habitat, poor nutrition, mites, diseases, other pesticides, etc. will continue to impact pollinators individually and collectively. Such an action may result in a loss of a pest management tool which may lead to increased use of other pesticides which could be more toxic to pollinators, humans, mammals, birds, fish and other non-target organisms.