Call for Pesticide Warning Label After Alarming Honey Bee Brood Loss
Guest Contributor
In modern agriculture, pesticides are often seen as precise tools designed to target destructive pests while sparing beneficial species. Yet a growing body of research suggests that one such tool, the insect growth regulator buprofezin, may be far less selective than once believed. Scientists are now calling for a pollinator warning label on buprofezin products, arguing that this pesticide could be contributing to severe honey bee brood mortality even at very low levels of exposure.
Buprofezin belongs to a class of chemicals known as insect growth regulators. Rather than killing insects outright, these compounds interfere with normal development so that larvae cannot mature into healthy, reproducing adults. For farmers dealing with pests such as whiteflies and mealybugs, which damage crops and spread plant diseases, this targeted developmental disruption has been a valuable strategy. The challenge is that beneficial insects, including honey bees, share similar developmental pathways that can also be affected.
Pollinator safety has become a central concern as researchers probe how buprofezin behaves in real-world conditions. Work led by Washington State University (WSU) scientists has raised particular alarm. A 2024 study out of WSU linked buprofezin exposure to what the authors described as “severe brood mortality” in honey bees. The research suggested harmful effects even at concentrations ten times lower than levels commonly measured in pollen, indicating that colonies might be vulnerable at doses once assumed to be benign.
At a recent meeting of the Washington State Beekeeping Association, WSU entomology professor Brandon Hopkins argued that buprofezin products should carry a pollinator warning similar to labels already required for certain other pesticides. He noted that these warnings can guide farmers on safer timing and methods of application, particularly avoiding use when crops are in bloom and attracting bees. Hopkins emphasized that better communication and education around buprofezin use could help reduce exposure without waiting for lengthy regulatory processes.
Buprofezin’s path into widespread use began in the 1980s, when it was developed by the Japanese agrichemical company Nihon Nohyaku. It received official registration in the United States in 2000 and was marketed under trade names such as Applaud. Farmers in California and Arizona were among the first to adopt it, primarily to control surging whitefly populations. Over the following years, its use expanded geographically and across crops. By 2018, data from the Pesticide National Synthesis Project indicated that more than 350,000 pounds of buprofezin were applied annually in the United States, particularly on tree fruits and cotton in regions including the West Coast, parts of the mid-Atlantic, Florida, and Texas.
For much of that period, official guidance suggested that buprofezin was relatively safe for beneficial insects. The U.S. Environmental Protection Agency (EPA) indicated that there were no restrictions preventing farmers from applying the pesticide to crops during bloom, and product labels even stated that it was “not harmful to beneficial insects.” Over time, however, studies began to challenge this assumption. Early research from the 2000s suggested potentially lethal effects on developing bumblebees and ladybugs, prompting a gradual reassessment.
By 2019, the EPA had instructed companies to remove the “not harmful” language from buprofezin labels. The agency’s preliminary ecological risk assessment concluded that adverse effects on nontarget insects, including pollinators, could not be ruled out. At least one chronic study on bee larvae was submitted to the EPA by the manufacturer Nichino, although that study has not been made publicly available. The EPA did not provide details when asked about it, while a statement from Nichino focused on alignment with regulations and a general commitment to ecological well-being.
The turning point for buprofezin and honey bee health came from field observations rather than laboratory theory. Hopkins and his colleagues did not initially set out to single out buprofezin. Their 2022 to 2023 project followed bees as they moved among different crops and pesticide regimes. It was only after observing “extreme levels” of dead bee brood inside and outside hives that the researchers began to suspect a specific culprit. According to lead author Ge Zhang, then a WSU assistant professor, they detected high buprofezin concentrations in pollen samples and recorded particularly high larval mortality shortly after pollination of fruit trees.
The published study concluded that high levels of buprofezin caused long-term harm to honey bee health. Colonies exposed under natural field conditions struggled to maintain their populations and could not produce enough new adults to replace losses, which led to colony failure later in the season. The authors described the situation as an alarming example of brood poisoning and called for more systematic monitoring of pesticide exposure in honey bees, as well as revisions to pesticide safety regulations.
Reed Johnson, an entomology professor at Ohio State University who was not involved in the WSU research, reviewed the work and described it as well conducted. He said it was entirely plausible that an insect growth regulator would damage honey bee larvae, noting that the observed effects are consistent with how such compounds are supposed to work on target pests. Although he stopped short of declaring the link definitive, he suggested the findings could help explain colony problems reported by beekeepers in treated areas.
Hopkins’ laboratory has since continued to investigate buprofezin with funding from the nonprofit Project Apis m. In one experiment, colonies were exposed to varying concentrations of the pesticide, including levels ten times lower than the field-relevant dose of 10 parts per million. The results, which are not yet peer-reviewed, again showed substantial brood loss. Between 64 and 79 percent of bees died in the exposed groups, compared with about 5 percent in the control group. Hopkins argued that such outcomes strengthen the case for a pollinator warning label that instructs growers to avoid spraying during bloom.
Regulatory responses differ significantly across regions. In the European Union, authorities have already moved to restrict and then fully ban buprofezin, although primarily out of concern for human health. In 2017, the European Commission prohibited its use on edible crops such as tomatoes and lettuce after research indicated that buprofezin residues could break down into aniline, a probable human carcinogen. More recently, the EU adopted a total ban, citing evidence that buprofezin is an endocrine disruptor in humans. Studies in laboratory animals associated the pesticide with increased thyroid weight, a potential sign of hormonal disruption and related health issues.
The European Food Safety Authority reported that it lacked conclusive data on endocrine disruption in insects and is not expected to seek additional pollinator data given the existing rationale for a full ban. In contrast, the EPA in the United States has not yet completed the re-registration process for buprofezin. The agency still needs to finalize an endocrine disruptor evaluation and assess potential impacts on plants and animals protected under the Endangered Species Act. That review is delayed, and under proposals in the 2026 Farm Bill, the EPA could receive a five-year extension to complete assessments for buprofezin and many other pesticides.
In the absence of new federal labeling requirements, some researchers and advocates see industry-led education as an interim safeguard. Hopkins suggested that grower groups in tree fruit and other sectors could coordinate voluntary guidelines to avoid spraying buprofezin when orchards are in bloom. Such approaches could consider overlapping bloom times of apples, pears, cherries, and other crops commonly planted side by side. Barbara Berardi Tadié of Pesticide Action Network Europe supported the idea of a warning label and even a complete ban on spraying during flowering seasons, emphasizing the importance of protecting pollinators that underpin food production.
Grower organizations in the United States have expressed general support for pollinator health, highlighting existing pollinator protection guidelines and collaborations with beekeeping and research groups. Apple producers, for example, point out that honey bees and other pollinators are indispensable to their crops and that they have a clear economic interest in sustaining healthy bee populations. As research on buprofezin and pollinator risk continues, education, careful timing of pesticide applications, and responsive labeling could all play roles in bridging the gap between crop protection and pollinator conservation.