SHADY COVE — Unseasonable weather has forced a delay in the scheduled aerial assault on the city's gypsy moth infestation.

SHADY COVE — Unseasonable weather has forced a delay in the scheduled aerial assault on the city's gypsy moth infestation.

Instead of a helicopter spraying biological pesticide over 336 acres early Tuesday morning, it was raindrops and snowflakes that took turns blanketing the area.

"We need a window of about six hours without rain for the pesticide to dry onto the foliage," said Dr. Barry Bai of the state's Insect Pest Prevention and Management Office [IPPM]. "Winds should be less than 10 mph and temperatures no lower than 35-38 degrees."

Tasked with detecting, controlling and eradicating harmful plant pests, the IPPM is a unit within the State's Agriculture Department.

"We look at the weather information and work with the Forest Service," said Bai. "They have a computer program that models the weather in the local area and makes predictions."

Based on those predictions, Bai said his office decided to reschedule the spraying to April 29. Two additional applications will follow at 10- to 14-day intervals.

"We're generally looking a couple of days ahead," he said, "and it's possible we may have to reschedule again if the weather is still bad."

Last week, signs alerting motorists of the gypsy moth spraying were posted along Highway 62 in the city.

If the current schedule holds, just after sunrise on April 29, a single helicopter will begin spraying a fine mist of bacillus thuringiensis of the variant kurstaki (Btk).

Btk is a collection of naturally occurring soil bacterium commonly used on tomatoes in gardens. It kills the gypsy moth during its caterpillar stage, by suppressing appetite and restricting movement.

Helmuth W. Rogg, IPPM program manager, said Btk is not a chemical pesticide and has been used safely and successfully for years.

"Btk is toxic only to susceptible caterpillars of moths and butterflies," he said. "It is not toxic to other insects, birds, fish, or mammals, including healthy humans, pets and livestock."

Bai said because Btk is organic it will not affect gardens or produce.

"We only use one-half gallon Btk per acre," he said. "That's not very much."

Bai said the helicopter is owned by a commercial operator and works under contract with IPPM.

"They will truck the helicopter to the site a day or two before spraying," he said. "Then they will do a reconnaissance from the air and set the corners of the spray area into their computers. That way they will be familiar with the area when they begin to spray."

Rogg said livestock, particularly horses, may be startled by the noise of a low-flying helicopter, possibly resulting in injury.

"We recommend that you confine your animals in a secure area prior to, and during, each application," he said.

The moths must be sprayed during their feeding stage as a caterpillar, which lasts from when eggs begin hatching in late March until roughly the end of June. An extended period of bad weather could jeopardize the project's success.

"We're a week behind now," said Bai, "but we still have time."

The 336-acre target area is generally south and east of the Rogue River, and west of Highway 62. Last year, 12 gypsy moths were trapped statewide, with six of those caught in a single trap hanging in a Shady Cove neighborhood.

IPPM scientists then realized they had a reproducing population of the moths and began planning an eradication project.

Bai said because gypsy moths eat the foliage on most trees and can destroy many acres in just a few weeks, the scientists want to act quickly before the population of moths becomes established and perhaps gets out of control.

"Our goal is to protect your beautiful trees," he said.

Complete spraying schedule information and updates are available toll free from IPPM at 1-800-525-0137.

Bill Miller is a freelance writer living in Shady Cove. Reach him at newsmiller@yahoo.com