Orchardists in Oregon’s Rogue Valley Turn to Healing Flame to Ward Off Diseases

By Anita Burke, Mail Tribune, Medford, Ore.

Jul. 9–A bacterial disease that attacks pear and apple trees in warm, humid weather has flared up in Rogue Valley orchards in recent weeks, and fruit growers are fighting back with flames.

Despite restrictions limiting potential sources of fire in forests, agricultural burning to stop disease in orchards has become a near daily occurrence, Jackson County fire districts report.

Burning infected branches is the best way to stop the spread of fire blight, which can destroy an orchard, said David Sugar, a horticulturist at Oregon State University’s Southern Oregon Research and Extension Center.

“There is a need for prompt destruction by burning,” he said.

Keith Emerson, director of orchard fruit production at Bear Creek Orchards Inc., oversaw a burn pile near Talent Tuesday.

He said crews started to see new growth on the trees that produce Harry and David’s Royal Riviera pears wilting and turning black with fire blight during the last two weeks of June, when temperatures were consistently in the 70s and 80s.

“This is usually beyond the infection period, but with the long, cool spring, it remained latent and is manifesting now,” Emerson said.

He said crews worked through the July 4 weekend, checking for damage every day, then removing and burning any infected branches.

The bacteria, native to North America, attack the trees through blooms or tiny injuries on green growth. Then it races down the tree from branch tip to root through the sap. Fire blight can kill a tree within days, linger for weeks, or form a canker where it dwells for a year or more until conditions are right for it to spread, Sugar said.

When trees are blooming, orchardists can spray them with antibiotics to prevent the blight bacteria from taking hold. When infections are active at this time of year, however, cutting and burning the blighted branches is the only way to stop the disease, he said.

“It’s critical to totally remove all of it,” Sugar said.

In humid weather, the bacteria produce a white, sweet-smelling ooze that attracts birds and insects, who then spread the blight to new trees. Extreme heat stops the oozing and pushes the bacteria into a dormant state, something orchardists hope this heat wave will accomplish.

In recent years, the Rogue Valley has had limited fire blight outbreaks that destroyed a few acres here and there, but the disease has the potential to kill vast sections of orchards. Washington orchards were badly hit in the 1990s and an epidemic in Michigan in 2000 wiped out 35 percent of the apple orchards there, he said.

Luis Balero, orchard superintendent for Associated Fruit Co., said fire blight killed at least 10 acres of the company’s trees three or four years ago and he hopes to prevent that kind of damage this year.

“It’s not critical yet, but quite a bit is showing up,” he said.

Crews are cutting and burning blighted branches regularly, trying to burn in the early morning when the fire danger is lowest and cooler conditions are best for workers, he said.

Emerson said the infected branches should be burned immediately because the bacteria can spread to new trees even from branches cut and stacked.

Orchard owners work closely with fire districts, Jackson County’s Health and Human Services Department’s air quality program and the state Department of Environmental Quality to plan burns.

“They need to burn and we can put in layers of safety conditions,” said Don Hickman, deputy fire marshal at Jackson County Fire District No. 3.

Both he and Darin Welburn, division chief at Jackson County Fire District No. 5, say they can’t remember any recent escaped agricultural burns.

Orchardists notify fire officials when and where they plan to burn, usually in a site reserved for destroying small piles of green branches, sometimes in the midst of an irrigated orchard. An area around the fire is plowed so no flammable materials remain. A water truck must be at the site and a person with a cell phone is stationed there to monitor the fire.

Morning burning, when temperatures are cooler and relative humidity is higher, also provides time for the fire to burn out, then be doused with water so no embers remain when afternoon temperatures soar and winds often pick up.

State law and county ordinances allow agricultural burning to control disease in the winter when air quality restrictions are in place, too.

—–

To see more of the Mail Tribune, or to subscribe to the newspaper, go to http://www.mailtribune.com.

Copyright (c) 2008, Mail Tribune, Medford, Ore.

Distributed by McClatchy-Tribune Information Services.

For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA.