In addition, he says, the widespread planting of genetically modified crops has allowed farmers to more effectively kill milkweed, the plant that monarchs need as caterpillars.
In March, conservation groups reported the smallest overwintering population of monarchs since their colonies were discovered in Mexico by scientists in 1975.
Taylor said he has so far persuaded about 7,000 gardeners to establish “waystations” for the monarchs. But with the loss of almost 200 million acres of monarch habitat over the past 20 years, he would like to see 7 million gardeners come to their rescue.
Mace Vaughan, pollinator program director for the
, a conservation group based in Portland, Ore., agrees. “To me that’s the core of pollinator conservation. If we tie enough [gardens] together, we can have a significant benefit.”
Providing nectar plants for monarchs, of course, will help other butterfly species. Other pollinators — notably honeybees and bumblebees — are facing problems of their own. Here, too, the gardener can make a difference by installing plants rich in nectar and pollen and by using pesticides carefully, if at all.
Sharon Metcalf lives in a cul-de-sac of townhouses in Bethesda, backing up to a grassy hillside and public woodland. She decided she would come to the aid of the monarch after watching the Imax film, “Flight of the Butterflies,” at the Smithsonian’s National Museum of Natural History.
She planted a bank of swamp milkweed across the hillside and then converted her little patch of lawn, adding nectar-rich perennials to some existing shrubs and planting additional milkweed among them.
She says the adult butterfly can detect milkweed plants from as far as a mile away. The butterfly lays eggs on the leaves, which hatch into hungry worms. Chemicals in the leaf make the caterpillars and adults distasteful to birds, and the striking markings of the caterpillar and the butterfly signal the fact.
“I was noticing fewer hummingbirds. I was getting turtles at some point, but they seemed to be disappearing. I was noticing in the lights at night fewer and fewer insects,” she said. “I realized if I wanted to create a healthier ecosystem, a good visible place to start is with monarchs, particularly because of their decline.”
Since she reworked her garden in early spring, she says, “I’m seeing things come back that I had lost.”
Replacing a small lawn with wildlife-friendly plantings might be enough for most of us, but a pair of tent-like cubes, three feet by two feet, attest to a greater effort: Metcalf is currently raising a brood of two dozen monarch caterpillars obtained through Taylor’s organization. They arrived the day I paid her a visit.
Several small plastic cups each held two or three caterpillars. Newly hatched, they were tiny — maybe a quarter-inch long and not much thicker than a cotton thread. They go through five molts before reaching pupating size. If you looked closely — she handed me a magnifying glass — you could see the distinctive patterning of black, yellow and white stripes.
Metcalf took a milkweed leaf she had harvested from the garden and placed it in one of the cups. The tiny creature went straight for it.
“I like to make milkweed sandwiches,” she said, demonstrating the technique. She places a leaf with the underside up. When a caterpillar crawls on it, she places a second leaf on top to allow it to munch away while covered. After a few minutes, the larva has made a discernible hole in the upper leaf.
As the caterpillars grow, so do their appetites, and Metcalf has to make sure they have enough milkweed: She sets a whole plant that she has dug and potted, and places it in each of the two zippered tents. Here they can develop into big caterpillars and then chrysalides without fear of being eaten.
The larvae take about 10 days to pupate and another 10 to 14 days as a chrysalis before emerging as a butterfly. Metcalf already has raised one brood this summer. She held a party for its release, first attaching a small identifying tag to each butterfly before its release.
The effort takes time, knowledge and equipment, and the kit comes with two full pages of single-spaced instructions. Taylor says the rearing program is an educational initiative geared more to schools than home gardeners, but there is little doubt that Metcalf is helping the monarch population.
For every 100 monarch eggs that hatch in nature, only one makes it to adulthood. Metcalf is counting on all two dozen of her charges taking flight toward the end of this month. “It could be these butterflies will move north or they’ll decide it’s time to fly back to Mexico,” she said.
Taylor also runs a tagging program for folks who want to capture migrating monarchs in a butterfly net and affix a sticker to their underwing. Since 1992, more than 1 million monarchs have been tagged, of which 16,000 have been recovered to provide scientific tracking of their migrations.
Running a kindergarten for butterflies and tagging them may be too much for most of us, but anyone with a bit of land can do something: “The average gardener just needs to plant eight or 10 plants to provide some habitat for pollinators,” Taylor said. “You don’t have to plant a whole garden.”
The decline of the honeybee has been one of the most publicized environmental disasters of the past decade. The sudden die-off and disappearance of whole hives, known as colony collapse disorder, is a phenomenon noted mostly by commercial beekeepers who ship their honeybees around the country to pollinate fruit and nut crops. But the hobby beekeeper, too, has seen levels of colony death unheard of in years past.
In May, a panel of scientists established to find the cause of CCD reported its finding: There is no single cause. The honeybee is beaten down by a number of viruses spread in part by a parasitic mite, called varroa, and by poor nutrition and pesticide exposure.
The panel said that honeybee colonies need more genetic diversity bred into them, and that more study is needed to determine the risks of pesticides.
Officials have said there isn’t enough evidence to follow a European Union ban on a class of systemic pesticides called neonicotinoids, which even in low levels can harm the ability of bees to navigate and forage, critics say.
One response by the home gardener is to keep bees, but this is a time-consuming hobby beyond gardening. Vaughan, of the Xerces Society, says the gardener can do more for the honeybee by providing plants rich in nectar and pollen and by avoiding pesticides.
Unlike honeybees, which came from the Old World with European settlers, bumblebees are native species that provide their own benefits to the gardener. They are better, for example, at pollinating tomatoes and blueberries than honeybees, and do a great job of pollinating squashes and cucumbers. They also can tolerate colder temperatures than honeybees. In addition to providing sources of nectar and pollen, the gardener can help the bumblebee by providing undisturbed, uncultivated areas of the yard where the bees can establish colonies, which may number 40 bees. (A honeybee hive can contain 50,000 bees.) Bumblebees may also nest in stone walls, unoccupied birdhouses or compost piles. Although they can sting, they rarely do. So if you find a nest, leave it alone.
Recently, a landscape contractor in Portland, Ore., sprayed linden trees against feeding aphids and managed to kill thousands of bumblebees.
There are ways of minimizing the risk, by not spraying plants in bloom and applying chemicals after bees have returned to their colonies at night. But the best way to conserve pollinators, according to the Xerces Society, is to avoid pesticides altogether.
Pyrethroids, which are commonly used against mosquitoes, kill many insects on contact, including beneficials. Of particular concern to pollinator advocates are neonicotinoids, which are relatively new and are now used extensively on plant-feeding pests. Among those registered are imidacloprid, acetamiprid and clothianidin.
Targeted pests include turf-feeding grubs, termites, leafhoppers, lacebugs and aphids. Bees can ingest neonicotinoids in nectar and pollen.
Separately, a study published July 24 by scientists at the Agriculture Department and the University of Maryland showed that when honeybees ingested pollen contaminated with fungicides, they were more likely to get a serious gut disease called nosema.
“Overall, we aren’t taking very good care of the little critters out there,” Taylor said. “These guys keep the system together.”
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