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WSU seeks to harness herbivore-induced plant protection odors

PROSSER -- Call it Nature's version of 9-1-1.

A tiny, two-spotted spider mite munching on the succulent leaf of a hop vine sets off alarm bells.

It's a silent warning, wafting out in the form of chemical compounds to nearby vines and beyond to creatures for which the spider mite is a tasty delicacy.

However, harnessing these odors isn't the stuff of science fiction lore.

Groundbreaking research is taking place right now near Prosser that could provide a whole new arsenal of weapons in the fight to defeat pests in a modern, planet-friendly way.

This relationship of mutual benefit between plants and predators is getting tested in the laboratory where David James wants to take it to the real world of hops and grapes and, perhaps one day, to all major crops grown in the Yakima Valley.

The Washington State University entomologist has spent more than five years conducting the only research of its kind in the world to understand this relationship and apply it to commercial crop production.

His research goes by the unusual acronym HIPPO -- herbivore-induced plant protection odors.

It's based on the bouquet of chemicals that plants emit when they are being attacked, sending out a plea for help and an alert to neighboring plants.

"It is really an amazing system. It is looking for every little bit of help it can get," he added.

Currently, James is focusing on spider mites and aphids in hops and a variety of pests in grapes, including leafhoppers and mealy bugs.

These pests suck sap from the leaves, turning them brown and reducing yields and the crop's quality.

If successful, the concept of enhancing a plant's defenses could lead to breakthroughs on how to manage pests for a wide variety of crops.

It also could further cement the movement of farmers toward more environmentally sensitive methods of controlling pests and diseases. Some of those moves have come about due to the loss of chemicals that kill all insects, products that are being forced off the market because of environmental concerns.

The goal to reduce use of expensive synthetic chemicals is an element of sustainable agriculture research under way by a variety of Washington State University researchers.

The university's Center for Sustaining Agriculture and Natural Resources has undertaken a variety of projects, with some long-term efforts using targeted approaches to control codling moths by using the pest's own sex attractant chemical to confuse male moths.

James said he defines sustaining agriculture as a way of reducing pesticide use by creating a balance in a commercial crop field, similar to what exists in nature where the diversity of insects keeps infestations in check.

However, reducing commercial sprays and saving farmers money still will come at a cost.

"You have to monitor more often and keep a closer eye on what is going on," he said.

Ann George of Yakima, administrator of the Washington Hop Commission, said the work has fascinating potential.

"The key is to figure out how much to put out and what is the best mechanism to put it out there," George said. "Then it starts to correlate to a commercially applicable system to get the beneficials attracted. This is one concept that if the system could be worked out, it would benefit hops and all crops."

It would not be, she cautions, the entire answer. But it would provide another weapon in the producer's arsenal along with the proper use of water and nutrients.

George's commission and another industry group, the Hop Research Council, are contributing more than $80,000 to support James' work. He also is being funded by the Washington Association of Wine Grape Growers.

One key to successful application in agriculture will be to lessen the amount of time it takes for beneficial insects to arrive after an infestation begins.

"All we are doing is finding out something to turn the plant onto its job earlier than it would usually do," James said.

James said different plants will release a different bouquet of compounds. One compound, in particular, is present in a number of plants when they are attacked. That compound, according to James, is among the blend of aromas released by at least 13 crop plants. Fortunately, it is already well-known and used in a number of industrial applications. It also is an ingredient in organic pest control programs.

The product is methyl salicylate, an ingredient that's found in toothpaste, BenGay rubbing compound, and Wint-O-Green Life Saver mints.

"Plants use the methyl salicylate to communicate among themselves. They call in predators and alert their neighbors that there are problems," he said.

Initial results have been impressive. The chemical compound attracted pest predators such as lady beetles, minute pirate bugs, big-eyed bugs and hoverflies to plots where dispensers containing the methyl salicylate were used.

James is now focusing his work at the WSU research and extension center near Prosser on what plants do when they are exposed to the methyl salicylate.

James said refining the system likely will consume the rest of his career.

That's based on the results of his work so far. They have opened up what he calls a Pandora's box of new questions on the effects of other compounds.

"It will take decades to work this out," he said.

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