by Eric Mussen
From March/April 2013 University of California at Davis, Bee News
For many years, beekeepers and environmentally interested individuals have expressed the opinion that the use of neonicotinoid insecticides (“neonics”) have interfered with the ability of honey bees and native bees to conduct their life activities properly. Since laboratory studies have detailed the disruptive effect on those insects, it was suggested that the same things were happening in the field. Unanticipated losses of formerly strong honey bee colonies, and easily observable decreases in bumble bee sightings, correlated well with increased use of neonics.
In Europe, registration and use of various pesticides are based on the “precautionary principle.” Basically, that means that a chemical is rated on its innate toxicity to honey bees and other non-targets, similar to the requirements of the U.S. EPA. Then, a second component enters the equation: likelihood of honey bees and non-targets to become exposed to the toxicant. This second factor is considered by EPA, but not as strongly as it is in Europe. If the sum of the toxicity and likely exposure is large enough, then the European Commis-sion can restrict or prohibit the product’s use. A report published by the European Food Safety Agency (EFSA) concluded that the neonicotinoid pesticides posed a “high acute risk” to pollinators, including honey bees, but that a definitive connection between the chemicals and loss of colonies in the field remained to be established.
The complaint against the neonics was brought to the European Commission a while ago, and the members originally voted that not enough scientific information existed to warrant a ban on the products. In the following appeal, the members voted to allow the Commission to prepare new restrictions concerning the use of the products. The restrictions are intended to accomplish two goals: 1) prevent large-scale environmental contamination by dust from agricultural planting equipment and 2) reduce exposure of honey bees and other flower-visiting insects to residues of neonics in nectars and pollens.
Beginning in December of 2013 or sooner, no more neonic-treated crop seeds will be sold or planted in the E.U. Neonics will be withdrawn from use by the general public. Neonics still may be used on plants that are not attractive to honey bees, or other foraging bee species, as forage plants (such as winter cereals).
What might we expect to see as results from this large-scale experiment? First, if large-scale contamination of the air through which bees are flying, contamination of weeds in agricultural fields, along the borders of the fields, and out in the environment no longer happens, then we would anticipate no longer hearing complaints about honey bees and bee colonies dying shortly after the plantings have taken place. Second, we might anticipate the problems of colony population depletion, sometimes to the point of colony loss, proposed to be due to exposure of bees to residues of neonics in nectars and pollens, would no longer be seen.
However, it is not likely to be that simple. The substantial losses, closely following neonic-coated seed planting, might drop off. But, other colony population problems may not become better for some time. Analyses of residues of pesticides in beeswax, stored pollens, and bees themselves in the U.S. suggest that there are myriad chemicals stored in the hives that are likely to be impacting honey bee physiology negatively already, including a few detections of very low levels of neonics. Since the neonics tend to persist in soil and woody perennials for prolonged periods of time, it is likely that bee exposure at low levels will persist. If the dosage levels of neonics that induce physiological impacts on honey bees are below current levels of detection (LOD), then it will be extremely difficult to determine this effect.
Additionally, removal of neonics from a significant segment of the market suggests that other compounds are likely to be substituted to control pests currently kept subdued by the neonics. Some of the older chemistries that no longer are available were losing their effectiveness against the pests due to selection for resistance, anyway. They are likely to be replaced by newer chemistries that may or may not have detrimental effects on exposed pollinators, including honey bees. The inadequacies in the U.S. to demand definitive, long-term studies on honey bee brood development and adult longevity, following exposure to sublethal doses of the compounds, means that we may find things will not be a whole lot better when we remove uses of neonics from our registrations. It will be interesting to watch this experiment unfold from a distance.