The U.S. Fish and Wildlife Service on Wednesday proposed listing the rusty patched bumble bee, a prized but vanishing pollinator once widely found in the upper Midwest and Northeastern United States, for federal protection as an endangered species.

One of several wild bee species seen declining over the past two decades, the rusty patched bumble bee is the first in the continental United States formally proposed for listing under the U.S. Endangered Species Act.

Named for the conspicuous reddish blotch on its abdomen, the rusty patched bumble bee — or Bombus affinis, as it is known to scientists — has plunged in abundance and distribution by more than 90 percent since the late 1990s, according to the Fish and Wildlife Service.

The agency attributes the decline to a number of factors, including disease, pesticides, climate change and habitat loss.

Bumble bees, as distinguished from domesticated honey bees, are essential pollinators of wildflowers and about a third of U.S. crops, from blueberries to tomatoes, said Sarina Jepsen of the Xerces Society for Invertebrate Conservation, which petitioned the government for protection of the insect.

Bumble bees’ annual economic value to farms is estimated at $3.5 billion, according to experts.

The rusty patched species is one of 47 varieties of native bumble bees in the United States and Canada, more than a quarter of which face a risk of extinction, according to the International Union for the Conservation of Nature.

Population declines among wild bees are much more difficult to document than those in honey bees, which are for the most part managed commercially and whose numbers are carefully tracked by beekeepers, Jespen said.

Jepsen said protections proposed for the rusty patched bumble bee will intensify the debate over the degree to which so-called neonicotinoid pesticides, routinely used in agriculture and applied to plants and trees in gardens and parks, have contributed to the decline of native bees.

“Endangered Species Act safeguards are now the only way the bumble bee would have a fighting chance for survival,” she added.

The Fish and Wildlife Service last year proposed protections for seven types of yellow-faced, or masked bees, in Hawaii.

The public comment period initiated by Wednesday’s proposed listing runs through Nov. 21, 2016, after which the agency could revise its proposal or finalize a decision.

KEYWORDS nature, agriculture, animals, endangered