Neonicotinoids were first introduced in the 1990s, and are now the most used synthetic pesticides in the world.

They can be used on leaves, in the soil and also as seed coatings — the third being the most common usage. The global market hovers around $2.6 billion and is dominated by two players: Bayer, which produces imidacloprid and clothianidin, and Syngenta, which produces thiamethoxam.

All three synthetic pesticides have been temporarily restricted in the European Union amid concerns about their impacts on bees. Legislation introduced by Rep. John Conyers Jr., D-Mich., and Earl Blumenauer, D-Ore., would temporarily ban four nitro neonicotinoids — the above three as well as dinotefuran — until the Environmental Protection Agency completes a new review of safety.

Neonics are broken down into two classes, nitro and cyano. The nitro class is thought to be especially damaging to pollinators such as bees.

While the Conyers-Blumenauer legislation is gaining some traction, passage is a long way off. Bee researchers say that neonics are just one of many factors weakening and killing bees, and Congress should focus on other avenues.

Marla Spivak of the University of Minnesota, one of the country’s leading bee researchers, recently attended a White House summit on pollinator health.

Here’s her wish list:

Provide long-term funding for diagnostic labs at a national level

Require the EPA to label urban landscape pesticides. While agricultural pesticides have clear bee warning labels, pesticides used by homeowners and landscapes in urban and suburban settings are unregulated.

Provide funding for plantings along rights-of-way — near roads and utilities — to provide corridors for bees.

And, “of course, more funding for research,” Spivak added. “But that’s always a given.”