Imidacloprid Found to Impact Bees

from USDA

Last Wednesday, January 6th 2016 the U.S. Environmental Protection Agency (EPA) in combination with Canada’s Pest Management Regulatory Agency released their preliminary pollinator risk assessment for Imidacloprid, the active ingredient in Bayer’s Gaucho insecticide. The preliminary risk assessment was about honey bees and the potential role that Imidacloprid may have on honey bee colony collapse. The current preliminary risk assessment identified that a residue level for Imidacloprid of 25 parts per billion or greater poses risk to hives when the pesticide comes in contact with certain crops that attract pollinators- specifically cotton and citrus. The impact to hives include decreases in pollinators as well as less honey produced and may be a factor in the die off of honey bee hives that has been termed Colony Collapse Disorder.

In 2015, EPA proposed to prohibit the use of pesticides that are toxic to bees, including the neonicotinoids class (Imidacloprid is just one example), when crops are in bloom and bees are under contract for pollination services. The Agency temporarily halted the approval of new outdoor neonicotinoid pesticide uses until new bee data is submitted and pollinator risk assessments are complete in December 2016.

Recent studies at the University of Maryland published in the journal PLOS ONE, looked at the effects of Imidacloprid on honey bee colonies over a three-year period. They found that Imidacloprid does not significantly harm honey bee colonies at real-world dosage levels. However, the scientists believe that a synergistic combination of many factors is most likely to blame for bee colony declines including climate stress and malnutrition. With CCD at a crisis level, the Whitehouse has developed a National Strategy to Promote the Health of Honey Bees and Other Pollinators and the EPA is no longer willing to tolerate any measurable impact on honey bees.

Imidacloprid is the most widely used insecticide in the world. Its use in the past has been unrestricted because it is very safe for humans, an order of magnitude safer than organophosphates, and a likely substitute. Imidacloprid is widely used by cotton producers and citrus growers. Insecticides in the neonicotinoid class are chemically derived from nicotine.

After examining the insecticide's use in all crops, the EPA's preliminary risk assessment concluded that bees are most at risk of exposure to damaging levels of the Imidacloprid from foliar and seed treatments in cotton fields and foliar applications in citrus fields. There is some dispute in the entomology science community as to the actual role of Imidacloprid in damaging bee colonies, but as stated above stopping Colony Collapse Disorder is one of the goals of the Administration.

Bees are used for the pollination of commercial crops. Pollination, the delivery of the male gamete of a plant to the female stigma of the same species of plant, is essential for fertilization and for the plant to produce seeds and fruit. Without pollination there would be no fruits, no vegetable and no seeds. Though, grasses, conifers, and many deciduous trees are wind-pollinated, most flowering plants need birds and insects for pollination. The vast majority of plants are pollinated by insects, and bees are responsible for the vast majority of pollination. Commercial agriculture uses honey bees raised to pollinate its crops. A Cornell University study estimates that the value of honey bee pollination in the United States is more than $14.6 billion annually.

During the winter of 2006-2007, a large number of bee colonies died out, losses at the impacted beekeeping operations were reported to be from 30% to 90%. While many of the colonies lost during this time period exhibited the symptoms from parasitic mites, many were lost, from unknown cause. The next winter, the number of impacted honey bee operations spread across the country. Honey bee colonies died out at even higher rates. The phenomenon was termed Colony Collapse Disorder.

No disease or cause was identified, the adult honey bees just seemed to disappear with very few dead bees found near the impacted colonies. The impacted colonies had low levels of parasitic mites and minimal evidence of wax moth or small hive beetle damage. The other active bee colonies did not steel the food reserves, instead they avoided the impacted hives. Often there was still a laying queen and a small cluster of newly emerged attendants present, but no adult bees.

Though the scientific literature has several mentions of honey bee disappearances—in the 1880s, the 1920s, and the 1960s, and the descriptions sound similar to Colony Collapse Disorder, there is no way to know if those colony collapses were caused by whatever is causing  Colony Collapse Disorder, and there is no end in sight to the current crisis. Colony Collapse Disorder is spreading around the world, and we may end up with insufficient numbers of pollinators to fulfill the demands of our agricultural industry. In 2012, 31% of the U.S. honey bee colonies were wiped out. The year before that it was reported as 21% of colonies lost. These losses if they continue could have a catastrophic impact on agriculture. One third of all food eaten in the United States requires honey bee pollination.

With Colony Collapse Disorder perceived to be at a crisis level, the Whitehouse developed a National Strategy to Promote the Health of Honey Bees and Other Pollinators in 2012. That strategy includes reducing honey bee colony losses during winter (overwintering mortality) to no more than 15% within 10 years. Thus, the EPA is no longer willing to tolerate any measurable impact on honey bees. There is a potential risk to pollinators with any insecticide.

The 60-day public comment period will begin upon publication in the Federal Register. EPA may revise the pollinator assessment based on comments received but plans to take action to reduce risks from the insecticide. The imidacloprid assessment is the first of four preliminary pollinator risk assessments for the neonicotinoid insecticides. Preliminary pollinator risk assessments for three other neonicotinoids, clothianidin, thiamethoxam, and dinotefuran, are scheduled to be released for public comment in December 2016.