The Pied Piper of Hotchkiss

Research lets nature work for the farmer

You could call Rick Zimmerman, research scientist at the Rogers Mesa Research Center, the Pied Piper of Hotchkiss. But instead of piping rats out of town, he gets bad insects out of orchards. And instead of a flute, he uses the insects' own chemicals against them.

Take earwigs. They've been a real problem this year, especially in organic peach orchards. When he tried the biological insecticides Neem and Pyrellin, "They laughed at me," Zimmerman says. So, he wrote a whole new tune just for them. "During the day, earwigs like to hide out with their buddies. They release a chemical, or pheromone, so they can find each other." Zimmerman drilled holes in PVC pipe, baited it with wheat bran and assorted essential oils, and hauled away earwigs by the thousands. He's the one laughing now.

Then there's the codling moth. This is the number one pest of apples in Colorado, costing individual growers thousands of dollars every year.

When a female moth is ready to mate, she emits puffs of a sex pheromone to attract male moths. For some years now, apple growers have used pheromone-treated twist-ties in their orchards. These look very much like the ties you find on plastic bags of bread or produce – just bigger. But attatching them to individual trees is labor intensive and they can be expensive, up to $110 per acre per year for just the pheromone.

Zimmerman has been testing man-made "puffers" that emit clouds of this sex pheromone. This lays so many false trails for the hapless male moths that many die before they ever find a female to mate with. While the puffers cost $60 to $70 each, growers may need only two or three per acre. Puffers can last many years, needing only refills each year.

Pheromone-based pest management costs less than conventional programs, and it has a secondary benefit as well: It doesn't kill insect predators. Growers not only don't have to spray for codling moths, they don't have to spray as much for other pests either, such as aphids and leafhoppers, because insect predators are still alive to do their own number on the bad guys.

Pheromones aren't the only song in Zimmerman's repertoire. He also plants flowers to encourage beneficial insects. Syrphid fly larvae eat a lot of aphids. The adults, however, feed only on nectar and pollen. By planting flowers for the adults, Zimmerman thinks he can entice them to hang around the orchard longer and lay more eggs, which hatch into more larvae, which eat more aphids. "Ideally," he says, "something will be in bloom from April until September."

He's also trying out a species of parasitic wasp. Originally from Kazakhstan, it has parasitized up to 50 percent of the codling moths in other apple-growing areas. Unlike pheromones, this control method should also help reduce codling moths in urban areas adjacent to orchards.

Research into soil ecology is a natural next step for Zimmerman. Working with John Moore and Jennifer Doles at the University of Northern Colorado, as well as Colorado State's Jessica Davis, he wants to see what soil critters live in orchards, both organic and conventional, and in native or uncultivated areas. What are the populations of harmful and beneficial insects and other organisms? How can they be manipulated to reduce orchard problems? How does the soil food web affect the flow of nutrients to plants, and can that be turned to the grower's advantage?

"The whole idea," says Zimmerman, "is to get nature to work for the farmer. I've never met a grower that likes to spray. Insect and disease problems are biological in nature, and ultimately, that's how they'll be solved."