Tens of millions of monarch butterflies are stretching their wings, preparing for the long annual northern migration from their overwintering grounds in Mexico to breeding grounds ranging from the Midwest to the East Coast.
Many will trickle into Hampton Roads by early June.
But biologists and conservationists are worried: Will those monarchs have a home to flutter back to?
The common milkweed plants on which monarchs lay their eggs, and which are the only food source for their caterpillars, are being wiped out by herbicides and mowed down by homeowners and municipalities with abandon.
That, in turn, has led to plummeting monarch population rates so alarming that two conservation groups just sued the federal government to get monarchs declared a threatened species.
Efforts are underway to boost the population by protecting milkweeds — from urging gardeners to go native, to devising incentives for farmers to leave milkweeds alone, to road trips planned this summer by biologists and students at the College of William and Mary in Williamsburg to collect milkweed samples for DNA and chemical analysis.
Those road trips are funded by a $20,000 grant from the National Geographic Society.
“To conduct a broader survey of milkweed across its entire geographic range,” said biologist Joshua Puzey. “Over this next year, I think we’ll likely find some very exciting things.”
‘How local is local?’
New numbers released last month by the World Wildlife Fund Mexico show the monarch population has rebounded to 150 million — more than three times the 42 million of the previous year, but still a 32 percent decline from its 22-year average and a 78 percent decline from the highs of the mid-1990s.
Last year’s count was also the second-lowest since the annual survey began in 1993.
Experts credit this year’s boost to favorable weather during the 2015 summer breeding season. While the monarch population does fluctuate with changing weather, experts still blame its overall decline on milkweed loss, especially in the agricultural Midwest where most monarchs are born.
Not only is milkweed critical habitat, it also contains a toxic chemical compound that the caterpillars absorb and use to repel predators.
“What’s amazing about the monarch is it has evolved to be resistant, to tolerate that chemical,” said Puzey. “And not only tolerate that chemical, but actually repurpose it.”
He and his colleague Harmony Dalgleish have been collecting and sequencing milkweed DNA as part of the larger Monarch Larva Monitoring Project. Now Dalgleish and one or two students will strike out in June and July on three road trips from the Dakotas to Texas to New England to the deep South to gather even more samples.
Understanding how common milkweed differs from region to region will help in replanting efforts, Puzey said.
“It answers the question, how local is local?” Puzey said. “There’s a population in New York — can you plant that in Vermont? Or if you replant in Virginia, do you need Virginia plants?”
Road blocks
Saving the common milkweed isn’t always simple.
For one, milkweed-killing herbicides are considered standard practice in modern agriculture.
“Farmers basically spray their field in the spring before they plant, and they’re using genetic strains of plants now that are resistant to herbicides,” said Fred Farris, deputy director of the Virginia Living Museum in Newport News.
“After their plants come up, they spray again with an herbicide the plant cannot be injured by, but it kills all the other plants. So it’s kind of a monoculture now in the field, whereas in the old days weeds were coming up along the edges and in the rows.”
The museum holds a Monarch Fest every October when monarchs are migrating south. It also hosts a butterfly garden and monarch display where visitors can watch butterflies undergo metamorphosis. The museum tags and releases some monarchs, and many have even made it to Mexico, Farris said.
To discourage herbicide spraying, the Environmental Defense Fund is creating a “habitat exchange” program that would pay farmers — as well as ranchers and forestland owners — to maintain or even seed milkweed on their lands, especially along the migration corridor. That program could launch by the end of 2017.
Homeowners that might want to help by planting milkweed in their gardens could face some hurdles: Nurseries rarely carry milkweed plants, and those that do will usually sell not the common milkweed but a tropical milkweed, Farris said.
“It’s beautiful and it grows easy,” Farris said. “(But) it’s not native.”
Even worse, tropical milkweed has recently been found to carry a disease that’s fatal to monarchs. “It’s a huge, huge problem,” he said.
Wilder patches
State and federal agencies are increasing efforts to preserve milkweed habitat.
The National Park Service refrains from mowing portions of the Blue Ridge Parkway, for instance, and the Virginia Department of Transportation does the same at some state sites as part of its Pollinator Habitat Program.
According to Jenny O’Quinn at VDOT, the agency is expanding that program to build more pollinator way stations at roadside rest areas and welcome centers, seed medians and roadsides with native pollinators and build naturalized gardens and meadows.
Meanwhile, homeowners who want to grow milkweed can plant seeds, snip and replant small root sections from existing plants, or seek out nurseries or garden clubs that sell them.
The Save Our Monarchs Foundation offers free seeds on its website of the swamp milkweed, which Farris said is also considered a native variety.
The root method is simple, Dalgleish said: In April as plants are beginning to sprout, dig up small pieces of root buds, replant them, and the new plants should be ready when the monarchs arrive.
Meanwhile, VLM sells common milkweed plants at its native plant sale in the spring and fall. The next sale is set to for the weekends of April 16-17 and April 23-24.
Native milkweed is hardy and reproduces rapidly, Farris said.
“It’s not going to look like a formal, clean garden,” he said. “People are going to have to accept some wilder patches, which is better for all insects and butterflies and wildlife (and) why we support native plants so much.
“It’s unfortunate everybody’s accustomed to gardening with mostly nonnative plants that they get at nurseries. They’re beautiful, but they don’t feed native insects. Insects have evolved to feed on specific plants that grow here, and if we eliminate them and just plant these nonnative plants, we’ve created a desert — not just for the monarchs. It’s a beautiful, flowering desert with big patches of green grass and no insects. Nothing hardly living there.”
Dietrich can be reached by phone at 757-247-7892.
