What are neonicotinoid insecticides?
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
What initiated the special registration review of neonicotinoids?
Concern over how the use of neonicotinoid insecticides may affect insect pollinators led the legislature to request that the MDA report on the process and criteria needed to review neonicotinoid use and impact in Minnesota. The report needed to address both the current and future impacts. The Commissioner of Agriculture directed MDA staff on November 5, 2013, to initiate a special review of neonicotinoid insecticides on insect pollinators.
Who was involved in this review of neonicotinoids?
The MDA sought input from several interested stakeholders, including beekeepers, academics, citizens, farmers and their suppliers, and pesticide registrants. The MDA also 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 for use in the review. The MDA collected and reviewed a significant amount of information and peer-reviewed research related to neonicotinoids and pollinators.
What criteria did the MDA follow to carry out the review?
The MDA has a well-established process and criteria to conduct a variety of pesticide reviews. Previously, the MDA 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 prior 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:
- Neonicotinoid background, chemistry, and mode of action;
- Federal, state, and other neonicotinoid registration policies and initiatives;
- Neonicotinoid use and sales;
- Neonicotinoid applications and movement in the environment;
- Risks of neonicotinoid use; and
- Benefits of neonicotinoid use.
Why do Minnesota farmers choose to use neonicotinoids?
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. The neonicotinoids are systemic insecticides, meaning that they are absorbed into the tissue of the plant and can therefore impact feeding pests. Farmers 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 be controlled easily by non-systemic insecticide sprays applied to the leaves and stems of the plant
What is the average use/sale of neonicotinoids in Minnesota?
In Minnesota, there are more than 500 registered neonicotinoid products to control soil or foliar (leaves and stems) pests. Total sale of neonicotinoid products in Minnesota from 2010 to 2013 was 381,300 pounds. The bulk (>99 percent) of neonicotinoid products sold from 2010 to 2013 in Minnesota were comprised of clothianidin, thiamethoxam, and imidacloprid. In comparison to all chemicals, neonicotinoids accounted for 0.05, 0.12, 0.06, and 0.09 percent of all chemical products (all chemistries including nonagricultural pesticide products) sold in Minnesota in 2010, 2011, 2012, and 2013, respectively. Because, Minnesota 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.
Are all neonicotinoids equally toxic to pollinators?
No, toxicity of neonicotinoids depends upon several factors including active ingredient, pollinator species, formulation, application site, plant stage, application time, and environmental conditions.
What levels of neonicotinoid residues have been found in plants and are they lethal to pollinators?
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.
Through which routes may pollinators be exposed to neonicotinoids?
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 drops of water released from the plant leaves (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.
How does abraded dust from neonicotinoid treated seed impact pollinators?
Abraded dust (i.e. that which is worn away) 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.
Can the MDA regulate neonicotinoid treated seeds?
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 US EPA’s exemption criteria are not subject to US EPA or MDA pesticide regulations.
Are there alternative insecticides to neonicotinoids?
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.
How long can neonicotinoids persist in the soil?
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.
What are state agencies doing to track the presence of neonicotinoids in water throughout Minnesota?
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. While 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 the EPA’s chronic aquatic life benchmarks for aquatic invertebrates.
How do neonicotinoids impact human health?
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.
Are neonicotinoids toxic to fish, birds, and other non-target organisms?
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.
What are the key findings of the review?
Executive summary of the review (PDF).
What actions are proposed as a result of the special registration review of neonicotinoids?
The following eight actions are proposed as a result of the special registration review:
- Action: Create a treated seed program (requires legislative action)
- Action: Create a dedicated “pollinator protection account” (requires legislative action)
- Action: Require formal verification of need prior to use of neonicotinoid pesticides, where appropriate
- Action: Develop an educational campaign for homeowners and residential users of insecticides
- Action: Review product labels for appropriate use of neonicotinoids for homeowners and residential users
- Action: Develop Minnesota specific pollinator stewardship materials
- Action: Increase use inspections for insecticides that are highly toxic to pollinators
- Action: Review label requirements for individual neonicotinoid products
What are some of the details of Action # 3?
Require formal verification of need prior to use of neonicotinoid pesticides, where appropriate.
Will the proposed actions result in increased use of pesticides more harmful to insect pollinators?
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.
How many bee-kill incidences in Minnesota were because of neonicotinoids in recent years?
In 2015, of the four bee kill incidences in Minnesota, neonicotinoids were observed in two cases. In 2014, there were six bee kill incidences reported in Minnesota, with neonicotinoids observed in one case.
How are other state agencies tracking emerging science on neonicotinoids and what actions are they taking?
Minnesota is the first state in the country to conduct 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 that effective January 1, 2018 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.
What are the US EPA’s introduced new label changes to protect pollinators from neonicotinoids? Are these changes enough to provide protection to bees from pesticides?
One of the major changes the federal US EPA 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 the US EPA has revised labels for foliar neonicotinoid products to clarify pollinator risks and restrict product application during flowering, questions remain about the ability of these label amendments to reduce impacts on pollinators.
Are there other countries where bee populations are declining allegedly due to neonicotinoid pesticides?
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.
What restrictions/regulations are imposed on use of neonicotinoids in other countries?
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. Further, Canada requires farmers to use a new corn and soybean seed lubricant called Fluency Agent for planting neonicotinoid treated seeds. At the provincial level, Ontario has implemented new laws effective 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 and proposed to ban these in 2018.
Would a ban on neonicotinoids help bee populations rebound?
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 that may lead to increased use of other pesticides which could be more toxic to pollinators, humans, mammals, birds, fish and other non-target organisms.
