Scientists say they have made a "breakthrough" that could lead to bee-friendly pesticides — but environmentalists argue that the only solution is to switch to organic alternatives.

The development is the latest in the ongoing debate over neonicotinoids, which are among the most toxic pesticides for bees and other insects.

Researchers from the University of Exeter's non-profit Rothamsted Research center and pesticide producer Bayer AG, say their findings, published Thursday, are key to production of pesticides that protect crops without causing harm to bee populations.

"This knowledge can help us avoid wasting time and money on pesticides that end up with use restrictions due to intrinsic bee toxicity," Chris Bass from the University of Exeter said.

Not all pesticides are the same

Use of neonicotinoids was restricted by the European Union (EU) in 2013. Last month, the EU's food safety watchdog confirmed that the pesticides harm bee populations. Several earlier studies have also shown that neonicotinoids affect the brains and bodies of bees and other insects, changing their behavior and reducing their fertility and lifespan.

But Lin Field, head of biointeractions and crop protection at Rothamsted Research, says pesticides shouldn't all be "tarred with the same brush."

A field is sprayed with pesticides

"Some neonicotinoids are highly toxic to bees but others have very low acute toxicity," she says. "Each insecticide needs to be considered on its own risks and merits, not just its name."

Understanding pesticide resistance

The research looked into why honeybees and bumblebees resistant to one type of neonicotinoid insecticide — thiacloprid — but not to others.

Bees have specific enzymes that help them safely metabolize the chemicals in insecticides. Researchers have now found that a particular subfamily of these enzymes — called CYP9Q — is responsible for the rapid breakdown of certain neonicotinoids.

"Identifying these key enzymes provides valuable tools to screen new pesticides early in their development, to see if bees can break them down," Bass said.

Ralf Nauen, insect toxicologist and lead investigator of the study at Bayer, said researchers will now be better able "to understand why certain insecticides have a high margin of safety to bees."

Still dangerous?

But not everyone is convinced. Dave Goulson from the school of life sciences at the University of Sussex, told DW his research, published last year found that thiacloprid does significantly harm bumblebee nests.

Watch video 01:01 Insecticides threaten bees

"Despite the lower toxicity to bees compared to some other neonicotinoid pesticides, there is evidence that thiacloprid use does harm bumblebee nests under field conditions," he said. "It is less toxic, but applied at a much higher rate."

Emily Marquez, a staff scientist at the Pesticide Action Network in North America, also says exposure to pesticides will still affect bee populations.

"Neonics are insecticides, and that exposure of insects to these chemicals overall isn't going to be beneficial to bees' health," she told DW.

"The extent of the effects of exposure to these complex mixtures is not well known," Marquez added.

Not all about bees

Keith Tyrell, director of Pesticide Action Network UK, a British charity that promotes alternatives to chemical pesticides, told DW that although more research is always welcome, the new study has "a bit of a narrow" focus.

"It's not just bees [that are affected by pesticides] — insecticides are designed to kill insects, so using them will inevitably disrupt ecosystems and lead to biodiversity loss," he told DW.

"We need to remember that there is a pattern here," Tyrell said. "We find a product, develop it, release it, then a few years down the line we discover there's problems."

A major study published last year in the peer-reviewed journal Nature Plants, showed that it is possible for farms to slash pesticide use without huge losses.

"We need to find a way to change our agricultural model, and switch to non-chemical pest control methods that work with nature. These techniques exist and are effective," Tyrell said.