Novel New Products Help Manage Fire Blight in Canadian Orchards

Fire blight, caused by the bacterium Erwinia amylovora, is a devastating disease of apples and pears. Many of our current cultivars and rootstocks are highly susceptible to fire blight. Combined with warmer, wetter springs, the risk of fire blight in any given year can be significant.

Until recently, apple and pear growers in Canada have been limited to the antibiotic streptomycin, in conjunction with cultural methods (e.g. Apogee, pruning, vegetative growth management) to manage fire blight. The potential for resistance to streptomycin is a growing concern. Copper sprays at green tip to reduce bacteria have been of questionable effectiveness and pose a phytotoxicity risk to the tree.

Two new bioantagonists, Bloomtime Biological FD and Blightban C9-1, were registered in Canada in 2007 for fire blight. These products both contain strains of a commonly occurring bacterium, Pantoea agglomerans, which compete with the fire blight bacteria on floral surfaces. Given sufficient time to colonize the blossoms, they prevent fire blight bacteria from establishing on those sites.
Once established, populations of bioantagonists become partially self-sustaining by spreading from blossom to blossom via insects and rain. To be effective, the antagonistic bacteria must stay active for at least 5 to 7 days during bloom.

In 2007 and 2008, EarthTramper Consulting Inc. conducted on-farm commercial trials in Ontario and Nova Scotia to demonstrate Bloomtime and Blightban. These products were applied at 20% and 75% bloom using airblast sprayers. Control blocks were untreated. Streptomycin was applied to all treatments where Cougar Blight and MaryBlyt showed "high" or "extreme" blossom blight risks.

Half the demonstration orchard sites showed a marked difference between the bioantagonist-treated sites and the control sites:

*Streptomycin was applied where models called "high" or "extreme" FB risk.

*Streptomycin was applied where models called "high" or "extreme" fire blight risk.

In 2008, Bloomtime was commercially available, at a cost about $130/acre for the recommended 2 applications. The reduction of the incidence and severity of blossom blight may well merit the price tag, especially during a warm, wet spring.

Bloomtime and Blightban C9-1 offer a valuable new approach to combat fire blight. These bioantagonists provide an effective alternative to copper, and complement the Cougar Blight and MaryBlyt models, streptomycin treatments and sound horticultural practices in an integrated approach to fire blight management in today's orchards.

Figure 1 - Shoot Blight (Courtesy of Bernie Solymar)

Funding for this project was provided by Agriculture and Agri-Food's Pest Management Centre (Project PRR07-340).

Related Links:

• Agriculture and Agri-Food's Pest Management Centre

  
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