Federal agencies need to patch some scientific holes in their ongoing efforts to protect struggling bee populations, according to the nonpartisan watchdog agency of Congress. The U.S. Department of Agriculture (USDA) lacks a plan for monitoring populations of certain non–honey bee species, a new Government Accountability Office (GAO) audit argues. And the U.S. Environmental Protection Agency (EPA) needs to collect data on pesticide mixtures to more accurately assess the risks bees face from the chemicals, GAO says.

Although USDA and EPA have taken “numerous actions to protect the health of honey bees and other species of bees,” beekeepers “continue to report rates of colony losses that they say are not economically sustainable,” the GAO audit says. “Finding solutions to address the wide range of factors that may affect bee health …will be a complex undertaking that may take many years and require advances in science and changes in agricultural and land use practices.”

The 11 March report highlights potential vulnerabilities in how the federal government is acting on recommendations unveiled last May by a multiagency task force convened by President Barack Obama. That task force called “for action, but the GAO report calls for monitored, responsible action,” wrote entomologist Marla Spivak of the University of Minnesota, Twin Cities, in an email. “I’m happy to see this … report and hope it is heeded.”

For about a decade, beekeepers have reported losing an unusually high number of their colonies each winter. Although scientists are still trying to pin down what’s behind the trend, researchers and agencies say it could stem from a combination of factors, from habitat loss to pathogens to pesticide exposure. The problem carries major implications not just for ecosystems but also for humans—bees and other pollinators help produce one-third of people’s food, government figures suggest.

The White House task force identified a series of policies that agencies should undertake to protect bees and other pollinators from pesticides and pathogens, preserve bee habitats, and promote bee-friendly plants. The strategy sets a number of targets, including cutting overwintering bee colony losses to 15% (from roughly 30% in recent years) by 2025. And it identified several areas of research that agencies should pursue, ranging from bee population and health monitoring, to environmental stressors, to bee conservation methods.

Moreover, the task force told agencies to make sure that wild and native bees weren’t left in the lurch. The task force had called on USDA to monitor populations of native and wild bees, not just managed honey bees. But the GAO audit found that USDA still lacks a plan to monitor non–honey bee populations.

In response, USDA Chief Scientist Catherine Woteki told GAO that it would be “physically and fiscally impossible” to track the roughly 4000 North American species of wild and native bees But she said it would be “informative” to monitor a smaller number of “sentinel species,” each of which could serve as a proxy for multiple bee species. She also said that citizen science could play a role in USDA’s bee monitoring efforts.

At EPA, the White House task force had suggested that the agency try developing ways to assess how mixtures of pesticides encountered in the real world affect bees, instead of solely assessing one compound at a time, as the agency does now. But the GAO audit suggests that EPA doesn’t yet have data on the most common pesticide mixtures and “does not know how it would identify them.” Data on the most common mixtures “are available and could be collected from farmers, pesticide manufacturers, and others,” GAO said, adding that the assessment of mixtures could help EPA “determine whether they pose greater risks than the sum of the risks posed by individual pesticides.”

GAO also suggested that EPA look into obtaining toxicity data from pesticide makers on how pesticides affect non–honey bee species.

Although EPA has in recent years updated its pesticide risk assessment methods to factor in a new suite of bee safety tests, the agency says it still doesn’t have the necessary standardized scientific procedures to quantitatively assess pesticides’ risks to non–honey bees or the effects of mixtures. Some new methods for measuring pesticides’ short-term toxicity to bumblebees and mason bees may soon be ready, EPA toxics chief James Jones told GAO.

Some mixtures may be useful to identify, he suggested. But many could be challenging to assess, he suggested, at least for now, as their formulations might vary from area to area. Another challenge is that the ingredients might affect bees through different mechanisms that no single test can fully account for.

The EPA said in a statement that it was still reviewing the GAO findings. USDA’s media office didn’t immediately respond to a request for comment.

At least one environmental group swiftly reacted to the GAO audit. “For far too long, the EPA has turned a blind eye to the impacts of pesticide mixtures,” Lori Ann Burd, of the Center for Biological Diversity’s Portland, Oregon, office, said in a statement. “I hope this report will force the agency to finally take the commonsense measure of studying the effects of pesticides in real-world conditions.”