July 6, 2008

Synthetic Pheromone Packets a Safer Way to Fight Mountain Pine Beetle Infestations

By Christine Weeber

Pesticides often have larger effects than we intend. Some of those used in responding to the mountain pine beetle infestation are no different. Carbaryl, the active ingredient in the most common sprays used to protect trees against beetles, is one of these. It is a neurotoxin that is dangerous to humans and pets through skin contact, inhalation and ingestion through food or water. And it is highly toxic to bees, stoneflies and some fish.

In 2005, 12 groups representing farmworkers, beekeepers and environmentalists called on the Environmental Protection Agency to cancel carbaryl due to the unreasonable risks associated with it. In 2007, the EPA restricted many pet and home uses of it.

Though carbaryl (trade names: Sevin, Tercyl, Adios, Carbamec) has been found in water supplies, both the U.S. Forest Service and Rocky Mountain National Park are spraying thousands of trees with it here in Colorado.

What risk does this pose to downstream water users? Forty percent of Boulder's water is from Barker Reservoir, so it is of great concern that the Silverthorne/Dillon Joint Sewer Authority declared they found carbaryl in the Silverthorne plant effluent (i.e., treated water) in 2007.

But there is an alternative. Pheromone packets, called Beetle Block, are a recently approved eco-friendly option. These contain Verbenone, a synthetic pheromone, and are hung on trees to repel beetles by sending a message that a tree has reached maximum beetle saturation. The EPA says there is no risk expected to humans or the environment from Verbenone.

The packets need to be placed on trees before the beetles fly in early summer. Beetle Block has been most successful when used as part of an overall plan to thin forests and remove infested trees, and when used in forests that are less than 20 percent infested. Though relatively less successful than carbaryl, Beetle Block is not toxic.

In three-year tests in Montana, the packets successfully protected trees from beetles. In another study, mass attack was reduced to an average of 3.6 percent; in untreated areas, 48.3 percent of trees were mass attacked. In 2005, the Bark Beetle Technical Working Group stated that Verbenone was effective in protecting trees in many instances from beetles.

Some homeowners have also placed mulch around the base of trees and used drip irrigation systems to water three to four times a month during warmer months.

If landowners do decide to spray, they should alert neighbors so they can close their windows and keep their children and pets inside. Please also post a sign so people know what trees have been sprayed. Rocky Mountain National Park posts signs for 60 days after spraying trees in the park (and people are kept 200 feet away from sprayed trees for at least 12 hours).

Originally published by Christine Weeber.

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