MINNEAPOLIS (WCCO) — It’s a ritual of spring: Monarch butterflies returning to Minnesota from their winter refuge in Mexico.

But there’s disturbing news south of the border. Scientists report a drop of nearly 60 percent in the number of Monarch butterflies making it to their winter home in Mexico this year — the lowest level since record-keeping began 20 years ago.

It doesn’t surprise a University of Minnesota expert.

“It makes me sad that, despite all these people caring, we still saw this precipitous drop,” said Dr. Karen Oberhauser.

NewsRadio 830 WCCO’s Steve Murphy Reports

Oberhauser says reasons include pesticides that kill the Monarchs’ main food source – milkweed. She’s encouraged, however, by the level of concern in Minnesota.

“Minnesota is a very important state for Monarchs. A lot of the population that migrates to Mexico in the fall has come out of Minnesota. So there’s a lot that we can do in this state to help preserve them,” said Oberhauser.

That would include planting milkweed and nectar plants in gardens and parks. The Monarch is Minnesota’s state butterfly.