Monarchs 'n Milkweed

Mar 12, 2014

Monarchs and milkweed are in the news again.

As well they should be.

The declining monarch population, coupled with the decreasing scarcity of their host plant, the milkweed, is disturbing. The larvae of the monarch butterfly (Danaus plexippus) feed exclusively on milkweeds. No milkweed, no monarchs.

Butterfly expert Art Shapiro, distinguished professor of evolution and ecology at UC Davis, says the problem hasn't totally reached California yet. "The 'dearth of milkweed' problem is primarily an East/Midwest problem, due to increased use of Roundup since the introduction of 'Roundup-ready' GM crops. It's quite real. There is no such problem out here--at least yet--but there is a new milkweed pathogen that may cause one! Dave Rizzo (UC Davis Department of Plant Pathology) and I hope to publish on it shortly. No harm in planting milkweeds, but the problem isn't a California one, at least not yet."

Journalist-photographer Alessandra Bergamin, writing in the Feb. 18 edition of Bay Nature: Exploring Nature in the San Francisco Bay Area, says that "the number of monarchs overwintering in Mexico's Oyamel fir forest has reached an all-time low," quoting the World Wildlife Fund in Mexico. "The reports suggest that factors such as loss of habitat, climate change and use of insecticides have contributed to the decline."

The situation in California, however, looked better than bleak last year. A little better. "Monarch butterfly populations in California's coastal overwintering sites showed a slight — and surprising — rebound in 2013 after more than a decade of dwindling numbers," Bergamin wrote. "The 2013 Western Monarch Thanksgiving Count tallied 211,275 monarchs at 162 sites from Sonoma County to San Diego County, up from 144,812 the year before."

Over the past two decades, however, the Western monarch population has dramatically declined in California, she pointed out in her article, "Western Monarch Population Hanging On."  The downward trend is expected to continue.

Meanwhile, the Xerces Society for Invertebrate Conservation, headquartered in Portland, Ore., has posted a seed finder resource so folks can find milkweed seed in their state and plant the seeds in their gardens, parks, landscapes, restoration areas and on farms. 

Oakland parks supervisor Tora Rocha is taking it one step further. She is collecting the monarch caterpillars, rearing them, and releasing the adults in the Lakeside Gardens at Lake Merritt.  Her newly formed Pollinator Posse has sparked the interest of volunteers, who range from school children to city council members. They all want to save the monarchs.

Rocha bans pesticides and herbicides from her pollinator gardens. “For the past fifteen years the gardens have had a pesticide-and herbicide-free policy,”  Rocha told writer Constance Taylor of Wild Oakland, which offers free, Oakland-centered environmental education.  “We also rely on volunteers contributing thousands of hours to keep our parks maintained--about 75% of the work is done by volunteers.”

Rocha says it's not enough to be a custodian of the land: it's important to be a steward of the land and protect the pollinators.  She's created a video, posted on YouTube, that explains what she and the other Pollinator Posse members do. 

Rocha and colleague Eddie Dunbar of the Insect Sciences Museum of California and a fellow Pollinator Posse member, recently visited UC Davis to share information with Shapiro and native pollinator specialist Robbin Thorp, emeritus professor of entomology.

Another person keen on butterflies is Sally Levinson of Berkeley, who writes a blog on butterflies and is publishing educational videos, including "Secret Lives of Monarchs" and "In the Company of Wild Butterflies."  As a graduate student at UC Riverside, Levinson studied with major professor Bruce Hammock, now a distinguished professor of entomology at UC Davis. (He maintains a joint appointment with the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center.)

As an aside, the Bohart Museum of Entomology at UC Davis offers a "Got Milkweed?" t-shirt spotlighting the monarch and its host plant. The work of doctoral candidate Fran Keller and Bohart volunteer/naturalist Greg Kareofelas, the t-shirt is  available online or at the museum, located in Room 1122 of the Academic Surge building on Crocker Lane.

Want monarchs? Plant milkweed.