(Beyond Pesticides, August 28, 2012) New research reveals that bats may be at greater risk from pesticide exposure than previously suspected. When foraging at dusk, bats can be exposed to agricultural chemicals by eating insects recently sprayed with pesticides. A study from the University of Koblenz-Landau in Germany reveals that bats, due to their long life span and tendency to only have one offspring at a time, are particularly sensitive to reproductive effects from pesticides.
The study, “Bats at risk? Bat activity and insecticide residue analysis of food items in an apple orchard,” published in Environmental Toxicology and Chemistry, details the health effects of bats foraging on insects in an apple orchard after it was sprayed with the insecticides fenoxycarb and chlorpyrifos. After field applications of the pesticides, scientists measured the remaining chemical residues on flies, moths and spiders for two weeks. The highest residues were recorded on leaf dwelling insects and spiders, while lower contamination was found for flying insects. Based on this data scientists calculated exposure scenarios for different bat species, each with different feeding habits, and found that those which fed off insects from the leaves of fruit trees to be most affected.
Researchers indicated that current European Union risk-assessments do not adequately consider these important pollinators when reviewing the safety of a pesticide (United States Environmental Protection Agency [EPA] risk assessments also do not consider bats specifically). The scientists based their risk-assessment formulas on those used for mice and shrews, but further noted that such formulas are not sufficient for bats because of their unique ecological characteristics.
Bats can live up to twenty years, giving the animals a much longer time for their bodies to accumulate toxic levels of pesticides. Additionally, researchers note, “their low reproductive rates (usually a single offspring per year) require high adult survival to avoid population declines and dictate slow recovery of impacted populations.” Lipophilic pesticides, those that can accumulate in fat tissue, are particularly dangerous to bats. During migration or winter hibernation, if bats consume large amounts of pesticide contaminated insects, when their fat stores are metabolized pesticide concentrations can reach toxic levels in the animal’s brain.
Organophosphate pesticides such as chlorpyrifos are highly toxic to humans and the environment. Chlorpyrifos is a frequent water contaminant and a long range toxin, exposing communities and polluting pristine areas far from where it was applied. Volatilization drift””the evaporation of the pesticide after application””is also part of the problem for chlorpyrifos. A 2009 study found the pesticide to have significant impacts on the growth and development of amphibians miles away from the site where it was first applied. A USGS study from 2007 concluded that the breakdown products of chlorpyrifos are up to 100 times more toxic than the original.
Chlorpyrifos is a neurotoxic insecticide that was banned from residential applications after EPA determined that cumulative exposure resulted in serious adverse health outcomes, especially for children. Short term effects of exposure to chlorpyrifos in humans includes chest tightness, blurred vision, headaches, coughing and wheezing, weakness, nausea and vomiting, coma, seizures, and even death. Prenatal and early childhood exposure has been linked to low birth weights, developmental delays, ADHD and other health effects.
Fenoxycarb, a carbamate class insecticide, is currently being voluntarily phased out in the U.S by its two registrants Syngenta and Whitmire Micro-Gen Research Laboratories. The chemical can still be used until the end of 2012 by Syngenta and the end of 2013 by Whitmire Microgen.
Fenoxycarb is toxic to fish and aquatic organisms. It is considered a likely carcinogen by EPA, and acute exposure in humans can result in sensory and behavioral disturbances, incoordination, headache, dizziness, restlessness, anxiety, depressed motor function and seizures. Severe intoxication may result in psychosis, seizures, and coma. Other symptoms may include wheezing, nausea, vomiting, diarrhea, ocular meiosis, muscle weakness, and salivation. The chemical has also been linked to illnesses in Gulf War veterans.
Our pollinators are at risk. In 2006, around the same time that honeybees started disappearing from their hives, a hibernating bat in a New York cave was discovered with a strange white fungus growing on its muzzle and wings. Since that first detection, white nose syndrome (WNS), a disease caused by the fungus Geomyces destructans, has spread across the United States. Like colony collapse disorder in honeybees, the direct cause of WNS is poorly understood. While this new research does not mention the role of pesticides in WNS, it does conclude that bats should be given greater consideration in risk-assessments for pesticide products. Not only can bats be exposed through their diet, but they can also encounter pesticides through drift and inhalation, as farmers often spray their fields at night to avoid harming honey bees.
Last year, Beyond Pesticides called on Congress to stop the spread of WNS, which has killed more than 5.7 to 6.7 million bats in North America. Bats with WNS exhibit uncharacteristic behavior during cold winter months, including flying outside in the day and clustering near the entrances of hibernacula. Bats have been found sick and dying in unprecedented numbers in and around caves and mines. In some caves 90% to 100% of hibernating bats succumb to the virus.
Insect-eating bats play an important economic role in agriculture and timber production. A 2011 study in the journal Science found that the value of bats’ pest-control services to agricultural operations in the United States ranges from $3.7 billion to $53 billion per year.
Researchers believe that the fungus arrived from Europe on the boots or gear of cave visitors. Those who visit caves are encouraged to wash all their gear carefully before reentering another cave in order to avoid spreading the fungus. The fungus has recently been detected as far west as Oklahoma and as far south as Alabama.
For more information on what you can do to protect our native pollinators, visit Beyond Pesticides’ pollinator protection page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.