Washington, DC–(ENEWSPF)–September 4, 2015. Research into neonicotinoid insecticides, a class of bee-toxic chemicals, and their effects on bees, needs to be more comprehensive in order to better reflect their global use, concludes a recent review of the current literature. The authors of the review state that despite considerable research efforts, there are still significant knowledge gaps concerning the impacts of neonicotinoids on bees. Since 2006, honey bees and other pollinators in the U.S. and throughout the world have experienced ongoing and rapid population declines. The science has become increasingly clear that pesticides (especially the neonicotinoid class of insecticides), either acting individually or synergistically, play a critical role in the ongoing decline of honey bees and wild pollinators. Neonicotinoids can be persistent in the environment, and have the ability to translocate into the pollen and nectar of treated plants.
The systematic review, titled Neonicotinoid Insecticides and Their Impacts on Bees: A Systematic Review of Research Approaches and Identification of Knowledge Gaps and published in the journal PLoS ONE, took a look at over 200 primary research studies in order to identify knowledge gaps. While there is a growing body of science examining the impacts of neonicotinoid use, knowledge gaps need to be addressed to better capture the full extent of the impacts these harmful chemicals have on bees. For example, studies on crops are dominated by seed-treated maize, oilseed rape (canola), and sunflower, but more needs to be known about the potential side effects on bees from the use of other application methods on insect pollinated fruit and vegetable crops, or on lawns and ornamental plants. Furthermore, most of the 216 studies conducted are in Europe or North America, so relatively little is known about neonicotinoids and bees outside of these regions. The authors add that because there is considerable variation in ecological traits across bee taxa, studies on honey bees are not likely to fully predict impacts of neonicotinoids on other species. Recommendations from the study authors include opportunities for methodological improvements, such as using information from field studies in laboratory approaches, as well as more studies that link effects at the individual level to mechanisms at the sub-individual level, and also to consequences for colonies and populations. The authors state that while bees are subject to multiple, interacting environmental pressures, such as the promotion by neonicotinoids of additive or synergistic effects when combined with pathogens or parasites, the importance of neonicotinoid-pathogen interactions under field-realistic conditions might have been overemphasized. However, there is still strong evidence that indicates neonicotinoid exposure can make bees more susceptible to pathogens.
New research into the consequences of neonicotinoid use are being published at an unprecedented rate. A recent study provided supporting evidence to previous work showing that sublethal doses of imidacloprid, a toxic neonicotinoid insecticide, impairs olfactory learning in exposed honey bee workers. A January 2015 study that also looked at sublethal exposure to imidacloprid found that it leads to mitochondrial dysfunction in bumble bees, which then negatively impacts navigation and foraging skills. For example, exposed bees will have greater difficulty in recognizing the smell of a flower, or how to find their way back to their colony, which in turn can affect the colony as a whole. Two other recent studies found that, not only does neonicotinoid exposure result in reduced bee density, nesting, colony growth, and reproduction, but also that bees actually prefer foods containing neonicotinoid pesticides, despite their adverse effects.
Although these data gaps need to be addressed, the link between widespread neonicotinoid use and pollinator decline is clear and grows stronger every day. Beyond Pesticides has long advocated a regulatory approach that prohibits high hazard chemical use and requires alternative assessments. While EPA announced a moratorium on new bee- and bird- harming neonicotinoid pesticide products and uses, farm, beekeeper and environmental groups, including Beyond Pesticides, have urged EPA to follow in the European Union’s footsteps and suspend the huge numbers of other bee-harming pesticides already on the market. We suggest an approach that rejects uses and exposures deemed acceptable under risk assessment calculations, and instead focuses on safer alternatives that are proven effective, such as organic agriculture, which prohibits the use of neonicotinoids. See how you can help through Bee Protective.
Sources: PLoS ONE, www.beyondpesticides.org
All unattributed positions and opinions in this piece are those of Beyond Pesticides.