So mankind adjusts and persists, finding new ways to fight back.
"People come to us and ask, Can you do this?'" says David Cuddleback, CEO and president of Enviro Protection Industries Company (EPIC), which recently responded to customer needs and developed an armadillo repellant. "Then you look at the science of repelling that creature. We have a whole base of substances we're familiar with. We know exactly what can be used safely, no chemicals, what's safe around humans, recorded safe by the USDA or EPA."
Insect management is not only important on its own level, but lessons from it can be applied elsewhere.
"In the insect world (the amount of research) is massive," says Michael Wagner, an assistant professor in the Department of Fisheries and Wildlife at Michigan State University. "Integrated pest management, that kind of stuff. Lots of universities have programs. That gets a lot of attention because crop production is very important here and around the world."
Wagner considers such insect research "an engine that works for others." His work, in fact, is based on the insect-control model. Researchers, he says, want the most environmentally responsible way to do the job, "which is not to eliminate the pests, but to limit the harm being done by these pests."
Wagner is applying that idea to his field of study, the sea lamprey. Researchers are using a synthetic version of a pheromone that stressed lampreys produce, an alarm substance, that warns other lampreys of impending danger. The parasitic eel-like vertebrates can then be manipulated – away from some streams and rivers and into others.
"The idea we're pursuing is called push-pull," Wagner explains. "It's a very simple, intuitive idea. When you're trying to manage pests, you're really managing crop damage. The push-pull idea is the simultaneous use of attraction and repellants. Push them away from your stuff (through the synthetic pheromone) and pull them into other areas where they can be controlled."
Elsewhere, the battle continues as other researchers seek ways to control pests.
Amar Grewal is president of Natura Products, a company with branches in the U.S. and Canada that manufactures a line of products that promote pest control by limiting the damage. A microbiologist and organic chemist who has worked in the field for more than 20 years, Grewal has designed a slow-release tablet that does double duty in the garden.
He uses denatonium benzoate, "basically the world's bitterest substance. You put it in the root system of any plant and it gets taken up (into the plant). That was a no-brainer. What we wanted to test was, Does it remain bitter or get broken down? In a nutshell, it stayed bitter."
The chemical makes plants – roses, hostas, tulips – unappetizing for deer and rabbits and other creatures. Then he doubled down by adding components that enhanced a plant's root system and also broke down organic matter around the plant. It was a fertilizer-pest control all in one.
"It's not just a repellant, it's a fertilizer, a soil additive, it works as an organic fungicide."
He eschewed the one-size-fits-all notion. When a study showed that the product kept aphids from roses, he tailored it for rose bushes. When he saw how the root application made the roots especially bitter, he did some tinkering and produced a groundhog and vole repellant.
Natura (deergone.com) now sells repellants for deer, rabbits, voles, groundhogs, dogs, cats, raccoons and squirrels, all based on the same technology.
The repellant industry has moved away from the chemical approach and toward more natural substances, says EPIC's Cuddleback. "When made well and used properly, they are easily as good, often better, than the old chemical approach."
Granular products work better than sprays, he adds. And all of EPIC's repellants are from the company's own recipes.
"Sprays are in the vicinity to 2 1/2 6 percent active ingredients. Our granulars can carry three times that, up to 20 percent of active ingredients. So we get a lot of stuff on the ground that throws out more smells. That's our approach to repelling."
There are products for deer, rabbits, moles, cats, dogs, gophers, snakes, voles and the aforementioned armadillos. EPIC (epicrepellents.com) is also working on analyzing the behaviors of 13 varieties of ground squirrels in the U.S. "We're close to these things," Cuddleback says. "But we're only going to put them out there when we're sure of them."
And then there's the big one: rodents.
"The state of the art is attempts – and it hasn't been achieved – to find repellants for rodents like mice and rats," he says. "That's hard to do because they're very persistent pests. I make no promises, but I've seen what's out there and we can do better than that."
Trichomes are hair-like outgrowths on plants that produce chemicals that can ward off pests. After decades of cultivation, today's tomatoes are lacking in trichomes, which in the wild produce acyl sugars. But research at Michigan State has identified the gene that helps in the production of these sugars. The goal is to genetically engineer cultivated tomatoes – and other plants in the solanaceous family, such as potatoes, peppers, eggplants and petunias -- so they can produce the acyl sugars that work as a repellant.