(Beyond Pesticides, November 12, 2015) The U.S. Geological Survey (USGS) recently performed the first-ever study of pesticide residues on native bee populations and found that they are exposed to neonicotinoid insecticides, as well as other pesticides, at significant rates. This study digs deeper into a question that was previously considered by a researcher who studied chemical-intensive apple orchards and linked a steep decline in wild or native bees to the application of pesticides. The USGS study broadens understanding about the effects of toxic pesticides to native bee species, expanding field research that has principally focused on managed honey bee populations.
The study tested for 122 different pesticides including bifenthrin, atrazine and chlorpyrifos, a chemical for which the U.S. Environmental Protection Agency (EPA) recently proposed to revoke all food tolerances in response to a court-ordered deadline. According to study findings, 72% of bees tested positive for pesticide residues, raising concerns for the potential for unintended pesticides exposures where land uses overlap or are in proximity to one another.
Residues of pesticides found in bees in the study include thiamethoxam, clothianidin, and imidacloprid, all of which are highly toxic neonicotinoids, a class of chemicals that have been linked to the global decline in bee populations by a large body of science. Neonicotinoids are especially harmful to honey bees, causing adverse effects on their ability to perform basic tasks necessary for survival, such as foraging and reproduction, as well as cause overall population decreases, findings that scientists fear may translate to native bee populations. Neonicotinoids also contaminate over half of urban and agricultural streams across the U.S. and Puerto Rico, according to a recent study by USGS that expands on a previous USGS report that found the chemicals to contaminate Midwest waterways.
The most common pesticide detected is the neonicotinoid insecticide thiamethoxam, which is found in 46 percent of the composite bee samples. Thiamethoxam, specifically, is used as a seed coating on a variety of different crops, a practice that has been found to have no role in reducing crop damage from pests, despite manufacturer claims touting the benefits of its use.
In 2014, EPA released a memorandum concluding that soybean seeds treated with neonicotinoid insecticides provide little or no overall benefits in controlling insects or improving yield or quality in chemical-intensive soybean production. The memo states, “In studies that included a comparison to foliar insecticides, there were no instances where neonicotinoid seed treatments out-performed any foliar insecticide in yield protection from any pest.” Also published last year was a report by Center for Food Safety refuting claims that neonicotinoids bring greater benefits than costs to farmers. In the report, researchers analyzed independent, peer-reviewed, scientific literature and found that the benefits of prophylactic neonicotinoid use via seed treatments are nearly non-existent, and that any minor benefits that did occur were negated due to honey bee colony impacts, reduced crop pollination by honey bees, reduced production of honey and other bee products, loss of ecosystem services, and market damage from contamination events. Furthermore, preliminary reports out of the UK find that the country is poised to harvest higher than expected yields of canola in its first neonicotinoid-free growing season since the European moratorium on neonicotinoids went into place in 2013.
The study also identified the presence of traditional agricultural operations as a factor in whether or not native bees tested positive for pesticide exposure. “We found that the presence and proximity of nearby agricultural fields was an important factor resulting in the exposure of native bees to pesticides,” said USGS scientist Michelle Hladik, Ph.D, the report’s lead author. “Pesticides were detected in the bees caught in grasslands with no known direct pesticide applications.” These bees were determined to have at least one of the pesticides measured, which indicates they are potentially exposed to pesticides applied to nearby agricultural areas. Pesticide concentrations and detections are generally less in bees collected in grasslands with a smaller percentage of active agriculture within one kilometer, which is the maximum foraging distance for native bees. As a result, it seems that the land cover surrounding the agricultural fields could be an important factor for consideration in conservation planning.
Farmers increasingly understand the benefits of employing hedgerows, which have been found to be an effective barrier against spray drift as well as reduce pesticide use by promoting biodiversity and providing habitat for natural pest predators. For more information on hedgerows and their numerous benefits, see Beyond Pesticides’ Pesticides and You article Hedgerows for Biodiversity: Habitat is needed to protect pollinators, other beneficial organisms, and healthy ecosystems.
It is important to note that the study performed by USGS was a reconnaissance study, making it an important first step, but not the last, in understanding the exposure of native bee populations to pesticides in relation to the surrounding landscape. Its preliminary findings will be used to design more focused research on exposure, uptake and accumulation of pesticides relative to land-use, agricultural practices and pollinator conservation efforts on the landscape, an important step for the approximately 4,000 native species of bees in the U.S. Native bees are responsible for pollinating native plants like cherries, blueberries and cranberries, and were here long before European honeybees were brought to the country by settlers. Many native bees are also efficient crop pollinators, a role that may become more important if honey bees continue to decline.
In light of the shortcomings of federal action to protect native pollinators, it is important to create pesticide-free habitats that provide safe havens for these important creatures, and there are several ways you can get involved. Take action by calling on EPA to suspend neonicotinoids now. You can also declare your garden, yard, park or other space as pesticide-free and pollinator friendly. It does not matter how large or small your pledge is, as long as you contribute to the creation of safe pollinator habitat. Sign the pledge today! Need ideas on creating the perfect pollinator habitat? The Bee Protective Habitat Guide can tell you which native plants are right for your region. For more information on what you can do, visit our BEE Protective page.
Source: U.S. Geological Survey (USGS)
All unattributed positions and opinions in this piece are those of Beyond Pesticides.