As new standards approach for organic apple and pear management, The Organic Center has released a manual to help guide U.S. growers on alternative options to control the contagious disease known as fire blight.

An infected fruitlet shows bacterial ooze from fire blight

In October, the currently approved fire blight antibiotic oxytetracycline will undergo a regulatory ban by the National Organic Standards Board, forcing growers who wish to maintain organic certification to explore alternative means of control.

Later, another favored control antibiotic, streptomycin, will also be phased out by the board.

The Organic Center guide, available in full here, features insight from apple and pear growers already practicing alternative methods, as well as emerging research on the disease.

The center has expressed concern for the future of organic pome fruit farming, in light of a recent farmer survey indicating that up to 70% of organic growers may transition to conventional farming under the new standards.

A non-antibiotic control method, being developed by the USDA-OREI, is set for release in 2015. Dr. Jessica Shade, director of science programs for The Organic Center, said the release date of the new treatment will temporarily leave farmers without a viable alternative.

"The interim year between approved antibiotics sunsetting and release of the OREI project findings leaves growers with minimal guidance and experience for non-antibiotic fire blight control," Shade said in a press release.

"It’s unfortunate timing, as organic apple and pear demand are at all-time highs. If U.S. production declines, organic apple and pear prices could spike, or imports from South America – where the disease is not present – could greatly increase."

For growers wishing to maintain organic certification, The Organic Center manual suggests orchard management practices with an integrated systems approach for prevention, including the possibility of lime sulfur blossom thinning sprays. In 2012, Blossom Protect was added to the list of approved organic products to prevent fire blight.

Copper-based products with lower metal content, to avoid russet, are also under development. One approved option is Cueva. In 2014, Previsto is also expected to gain registration under the Environmental Protection Agency.

The guide points out that organic apples and pears exported to Europe are already prohibited from antibiotic use. As a result, many U.S. growers have successfully development alternative treatments. Currently, a reported 20% of organic apple and pear growers in Washington State are EU compliant.

Currently, two fire blight-prone cultivars, Fuji and Gala, account for about 50% of U.S. organic apple production. The Organic Center said no domesticated apples or pears appear to be entirely immune to fire blight, although several varieties have been developed to decrease susceptibility.

Examples of apples with improved fire blight tolerance include Pristine, Williams Pride, Priscilla and Juliet. For pears, the Canadian line of Harrow pears also shows greater resistance, although no pear has been found to be entirely immune.

Although such varieties are promising, the guide points out that they do now offer short-term solutions for growers facing the upcoming regulation change.

Related story: U.S.: concern grows over fire blight treatment options

Photo: The Organic Center

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