You've probably heard about the United Nations science report issued earlier this year that estimates that 1 million species of plants and animals are at risk of extinction.
Many of those species are insects, small bugs most of us have never heard of. Except for the monarch butterfly, they don't have the popular appeal of giraffes or polar bears, but they are crucially important for human survival.
That's because insects "run the ecosystem," Doug Tallamy, a professor of entomology at the University of Delaware in Newark, Delaware, explains.
"Insects are not optional," he said in a phone interview. "It's not OK if they disappear. Insects are the primary drivers of our ecosystems. If they go, we go. There is no Planet B."
Tallamy is one of two speakers who will make presentations Saturday, Sept. 28, in Davenport during the fall garden conference sponsored by the Scott County Master Gardeners of Iowa State University Extension. The other is Rick Darke.
Both have appeared in the Quad-Cities previously, but conference organizers believe the men's message of what home gardeners can do to help birds, pollinators and other wildlife is so important that they are inviting them back. And although their overall messages haven't changed, their presentations will be all-new.
Why are insects so important?
Pollinator insects make possible one out of every three bites of food we eat, while other insects cause the decomposition of dead plants and animals (lest we be surrounded by dead bodies) while still others provide food for other creatures such as birds. Of the roughly 9 million species of insects on Earth, only about 9,000 harm humans by biting, carrying disease of destroying plants, Tallamy said.
The headlines of the past year, particularly "The Insect Apocalypse is Here" appearing in The New York Times in late December, have infused the issue of declining insect populations with fresh urgency.
Despite widespread habitat destruction that shows no sign of abating, regular home gardeners can make a difference for insects by growing the right kinds of native plants, Tallamy said.
"Worry about your own property, that's where conservation happens," he said.
The principle of host-specificity
Tallamy wants to make sure his audience understands that 90 percent of insects — such as monarch butterflies — are host-specific. That is, they lay their eggs on, and eat only, certain plants. A whole forest full of vegetation will not support them if the one specific plant they need is not there.
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That is because insects and plants evolved in tandem over time, Tallamy said. Insects native to this country need plants native to this country. Some plants support more insects than others.
Oak trees, for example, provide food for 557 species of caterpillars, prime food for birds. The native tulip tree supports 21 species of caterpillars. The ginkgo (from China) supports no native caterpillars, Tallamy said.
So if you're a homeowner who has to choose among plants, choose the one that will provide the most benefit, Tallamy suggests. High on his list are oaks, birches, poplars, hickories and pines.
Also, it is important to pick plants that will provide food all season — spring, summer and fall, with spring and fall often being sparse. For this, Tallamy recommends cottonwood, native willow and oak trees as well as goldenrod, native sunflower, native aster and evening primrose.
Important: pesticides, lights, flower stalks
Here are four more take-away points:
• The United States contains roughly 600 million acres "filled with big lawns and plants from Asia," Tallamy said.
"That's 32 percent of the country that COULD help insects, and that's without touching agriculture." This land includes residential and corporate-owned landscapes.
• Homeowners should stop using synthetic pesticides. "Homeowners use twice as much as agriculture," he said. "They think that if a little bit kills, then a little bit more will kill more. They're not concerned about expense.
"If homeowners hire a lawn care service, they likely get an application of herbicides and pesticides every time there is a treatment, and that's completely unnecessary. It all gets into the water supply."
• If you have night lights, put them on a motion sensor so they're not on constantly. Otherwise, insects that are attracted to light "will fly around and around and exhaust themselves to death, or they get eaten by bats or by birds in the morning," Tallamy said. "Millions of insects are killed at lights each night."
• In late fall, leave your flower stalks standing rather than cutting them to the ground because a lot of native bees overwinter in stalks, Tallamy said. It's best to leave the entire stalk, but if that's too much for you, leave at least 12 inches.
The other plus with leaving the entire stalk is that often it has a seed head at the top that can provide food for birds in winter.