- Author: Kathy Keatley Garvey
It's in the current edition of The American Entomologist.
The UC Davis team, captained by Mohammad-Amir Aghaee of the Larry Godfrey lab, included members Danny Klittich of the Michael Parrella lab; Jenny Carlson, Anthony Cornel lab; Margaret "Rei" Scampavia, Neal Williams/Edwin Lewis lab; and Ralph Washington Jr., Steve Nadler lab.
The UC Davis debate team was assigned the “con” side of the topic, “Neonicotinoids Are Causing the Death of Bees Essential for Pollinating our Food Crops. The Use of Neonicotinoids Should End.” Auburn (Ala.) University drew the “pro” side. UC Davis defeated Auburn University and then went on win the overall student debate championship in the six-team, three-topic competition.
The neonicotinoid debate drew widespread attention. Below are the summaries distributed here in open access, Creative Commons:
Neonicotinoids are causing the death of bees essential for pollinating our food crops. The use of neonicotinoids should end.
Washington State University
Honey bees, bumble bees, and solitary bees are among the important biotic couriers transporting pollen from the male anther to the female stigma of flowers, playing a fundamental role in the fertilization and fruiting of angiosperms. The mutualism between bee pollinators and flowering plants is essential to approximately 35% of global agriculture (Velthuis and van Doorn 2006, Klein et al. 2007) and critical to many aspects of native ecosystems worldwide. However, this critical link is threatened by the decline of bee populations. The source of bee decline is multi-faceted; suspected causes of colony collapse disorder (CCD) in honey bees include, but are not limited to, biotic factors such as parasitic mites, pathogens, and resource availability/diversity, as well as abiotic factors including climatic change, land-use change, pollution, and pesticides (Decourtye et al. 2010, Neumann and Carreck 2010, Kluser et al. 2011, Girolami et al. 2012). The decline of native North American pollinators has the potential to disrupt the integrity of ecosystems and agricultural prosperity (Cane and Tepedino 2001). Native bee decline could be due to a number of reasons: the establishment of monocultures and disturbance of their native habitat; disruption in the pattern of bloom; the replacement of native flora with crop plants; or widespread insecticide use (Cane and Tepedino 2001). Among the classes of insecticides registered today, neonicotinoids are one of the most used insecticides worldwide, and are at the forefront of the investigation to determine the contributing factors to CCD (Girolami et al. 2012).
Neonicotinoid insecticides are effective against a broad range of chewing and sucking insect pest species (Zhou et al. 2013) and are registered for use in a wide variety of crops, including cereals, corn, cotton, oilseed rape, sunflowers, and sugar beets. This insecticide can be applied as a highly effective systemic seed coating, in the form of foliar sprays, or incorporated as a soil drench (Elbert et al. 2008, Yang et al. 2008, Blacquiére et al. 2012). All neonicotinoids are agonists of the insect nicotinic acetylcholine receptor (nAChR) (Matsuda et al. 2001, Elbert et al. 2008), causing excitation of the nervous system, paralysis, and eventually death of exposed, susceptible insects. While neonicotinoids are generally considered selective for insects and safe against mammals and birds, beneficial arthropods are still susceptible. Beneficial insects can come in contact with neonicotinoids if they feed on contaminated plant tissues or excretions, or are consequently exposed to the insecticide by ingesting contaminated prey (Prabhaker et al. 2011). When applied according to label instructions, neonicotinoids are not likely to come into direct contact with blooms, reducing contact with pollinators. However, neonicotinoids are highly potent and effective systemically; this class is highly soluble in water and can be moved by the plant translaminarly (Girolami et al. 2009).
Because of the value of pollination services provided by bees, and the widespread use of neonicotinoids, it is critical that the role of these pesticides in pollinator decline be determined. This will allow for informed decisions regarding future use of this class of pesticides.
Julian Golec, Matthew Burrows, C. Scott Clem, Adekunle Adesanya, Zi Ye, and Olufemi Ajayi
Advisor: David Held
Overwhelming evidence points to neonicotinoids as a critical factor in population declines of honey bees, bumble bees, and solitary bees (Sandrock et al. 2014). Neonicotinoids are the most widely used insecticide in agroecosystems due to their systemic properties (Hopwood et al. 2012), yet the impacts of neonicotinoids on bees extend beyond their use in agricultural settings. In urban settings, neonicotinoids can be applied at rates 120 times greater than those approved for agricultural settings (Hopwood et al. 2012). As a result, treated plants retain unmetabolized, active residues in virtually all plant parts, including pollen, nectar, and guttation fluids (Girolami et al. 2009). The effects of neonicotinoids vary based on the duration (acute or long-term exposure), route of exposure (oral or contact), and the bee species tested (Hopwood et al. 2012). In addition to outright mortality of individual bees, there are also sublethal effects implicated that affect bees at the colony level. For example, decreases in bumble bee queen production, pollen foraging efficiency, worker size, the rate of larval development, and learning abilities have all been implicated as sublethal effects of neonicotinoids (Decourtye et al. 2004, Gill and Raine 2014, Whitehorn et al. 2012). Additionally, these chemicals have been documented to affect immune responses in bees, making them more susceptible to pathogenic infections such as viruses and Nosema microspores (Alaux et al. 2010). Moreover, synergistic interactions between neonicotinoids and fungicides have been documented (Iwasa et al. 2004), which may indicate interactive effects with other chemical classes, increasing the negative impact on bees.
Current risk assessment protocols regarding the impacts of neonicotinoids on honey bees are insufficient, as they are focused on acute toxicity levels and do not incorporate various routes of exposure (Blacquiére et al. 2012). Shockingly, assessments for native bees are virtually nonexistent (Hopwood et al. 2012). Due to these factors, the U.S. Environmental Protection Agency (EPA) has recently called for a review of the current protocols in order to develop new risk assessment parameters (EPA 2012). Ahead of the U.S., the European Union (EU) has temporarily banned the use of neonicotinoids until further research can address sublethal and synergistic effects (van der Sluijs et al. 2013). The U.S. should follow the efforts of the EU and temporarily ban the use of neonicotinoids before irreversible damage occurs to an already stressed food industry and an increasingly less diverse ecosystem.
Historically, the 1996 Food Quality Protection Act (FQPA) restricted the use of toxic organophosphates, which lead to the creation of a new and presumably “safer” class of insecticides: the neonicotinoids (van Steenwyk and Zalom 2005). However, research has primarily focused on the European honey bee (Apis mellifera L.), and a few native bees (e.g. Osmia lignaria Say). It has since been found that the neonicotinoids are not a suitable alternative to older chemistries (Abbott et al. 2008). By using precedents set forth by the FQPA, the U.S. should temporarily cease the use of neonicotinoids until their effects at both the individual and colony levels can be thoroughly understood. We believe that a temporary ban on this insecticide class will lead to the discovery of new and safer insecticides, ultimately replacing the neonicotinoids.
Mohammad-Amir Aghaee, Jenny Carlson, Daniel Klittich, M. Rei Scampavia, and Ralph Washington, Jr. University of California, Davis
Advisor: Michael Parrella
However, the relationship between neonicotinoid use and pollinator decline remains disputed. Neonicotinoids were registered as reduced-risk pesticides because of their insect-specific action and low mammalian toxicity (van der Sluijs et al. 2013). They were selected to replace the organophosphates, carbamates, and pyrethroids, which have known non-target effects on humans and wildlife (Fairbrother et al. 2014).
Acute and chronic studies have shown that neonicotinoids are toxic to honey bees and bumble bees (Blacquiére et al. 2012). However, numerous studies implicating neonicotinoids as a cause of honey bee losses are insufficient in rigor and depth. Studies testing toxicity at field-realistic dosages between 1-10 ppb have shown inconsistent results (Cresswell et al. 2012). In addition, not all neonicotinoids have the same level of toxicity to bees. Acetamiprid and thiacloprid have an LC50 that is five orders of magnitude less toxic than clothianidin, thiamethoxam, and imidacloprid (Brown et al. 2014).
In addition, many other factors have been documented as contributing to pollinator decline (United States Department of Agriculture [USDA] 2013). Varroa destructor (Anderson and Trueman), a mite that feeds on the hemolymph of pupae and adult bees, vectors deformed wing virus and is a principal component of colony declines. Acaricides used to control Varroa are ubiquitous in wax comb of honey bee hives. These chemicals have been shown to compromise immune response in bees, impair honey bee behavior, and reduce the number of queens (Boncristiani et al. 2012). Pathogens such as Nosema ceranae (Fries) have impacted domesticated honey bee colonies, and N. bombi (Fantham and Porter) has wreaked havoc on native bumble bee populations (Mayack and Naug 2010, Evans and Schwarz 2011).
The lack of adequate nutrition further stresses colonies (Naug 2009). This results from a combination of habitat fragmentation and land-use changes that reduce the amount of wild forage available to honey bee colonies during periods of low food supply. Native pollinator populations are especially sensitive to habitat fragmentation and loss (Potts et al. 2010). This problem is compounded by the increasing demand for pollination services in agriculture (Aizen and Harder 2009).
Pollination demand created by almond production exemplifies the synergy of all these factors against honey bees. Every February, over two million colonies are moved to California to pollinate the almond bloom. Colonies are placed in staging areas at high concentrations and fed artificial diets to supplement a lack of natural forage (Fairbrother et al. 2014). These are optimum conditions for transmitting viruses and mites between colonies.
The best approach towards addressing pollinator declines would be to improve management practices to protect pollinators in crops (USDA 2013). This includes banning certain application strategies such as seed treatments. To this end, regulatory agencies need to have stricter registration guidelines that incorporate more comprehensive bee toxicity data, such as sublethal and synergistic effects on colonies, for all pesticides and methods of application (Hopwood et al. 2012). It is very important that growers are also educated on the proper use of these pesticides, which will prevent accidental losses of honey bees.
There is no definitive scientific evidence that neonicotinoids are the primary cause of pollinator declines. Given the current state of knowledge, banning neonicotinoids is a premature and disproportionate response to a complex issue. This issue requires holistic scientific inquiry and interpretation, and cooperation among stakeholders. Any changes must be based on science rather than opinion, current trends, or fear.