Development of a Strategy to Implement Use of the Bacterial Antagonists, BlightBan C9-1 and Bloomtime, in the Management of Fire Blight in Apples

Project Code PRR07-340

Project Lead

Bernt Solymár - Earth Tramper Consulting Incorporated

Objective

To validate the use of fire blight risk prediction models for the timing of applications of bacterial antagonists; train consultants, government extension staff and growers on the use of new bacterial antagonists through demonstration trials and reduce the use of streptomycin

Summary of Results

Background

Fire blight is a devastating disease of apples, pears, and other species in the Rosaceae family. The pathogenic bacterium, Erwinia amylovora, enters primarily through open blossoms but may also enter through wounds and natural openings. Infected flowers lead to a loss of the current season’s crop. In response to competitive global market, Canadian apple growers have moved to newer cultivars and high-density plantings. Many of these cultivars, however, are also susceptible to fire blight.

For years, the management of the disease was based on applications of the antibiotic streptomycin. In 2006, two biopesticide products, Pantoea agglomerans C9-1 (Blightban C9-1) and Pantoea agglomerans E-325 (Bloomtime), both known as bioantagonists, were registered in Canada. These products offer an opportunity to incorporate biological control tools into fire blight management programs, potentially reducing the use of streptomycin applications and delaying the development of resistance within the pathogen population.

The goal of this 2-year, on-farm demonstration project was to allow growers in Nova Scotia and Ontario to gain familiarity and confidence in using Bloomtime and Blightban C9-1 in an integrated fire blight management program.

Approaches

In 2007 and 2008, trials were conducted in several apple orchards in Nova Scotia and Southern Ontario. Disease pressure was variable in these orchards. Pest management consultants monitored the phenological stage of the trees using prediction models and informed growers of spray timing for the biopesticides and streptomycin.

Applications of the products were made by growers using commercial air-blast sprayers with the equivalent of 1000 Litres per hectare (L/ha) of water. Up to 3 applications were made. Data collection consisted of counting blossoms and shoot blight incidence on 20 trees per replication, 21 to 28 days after petal fall, and after visual symptoms appeared. The timing was chosen to evaluate the spread of disease that resulted from blossom infections while avoiding subsequent infections due to insects, hailstorms and other trauma events.

Results

The on-farm demonstration trials produced diverse observations and results due to such factors as weather patterns, tree varieties and age, history of disease in the different sites, type of sprayer, and grower practices. Above normal temperatures in certain sites resulted in a rapid opening of blooms, from 20% open blossoms to 100% bloom in approximately 24 hours on apple trees. Under these conditions, only one application of the biopesticides could be made. In some other areas, unusually cool temperatures in one of the trial years caused prolonged bloom, with blossoms open for an extended period of 5 to 7 days. There were also sites with lack of fire blight infections in one of the trial years; therefore, no comparisons could be made for these orchards during these seasons.

Some promising results were obtained in Ontario. In 2007, Bloomtime and Blightban C9-1 provided similar levels of control as the commercial standard, Streptomycin. During the same year in one site, there were significantly more blossom and shoot strikes in the untreated block as compared with Blightban™ C9-1 treatment. In 2008, dramatic differences were found in two sites between the untreated and the Bloomtime-treated plots, suggesting high efficacy of the biopesticides.

Results from Nova Scotia showed the number of trees exhibiting fire blight symptoms was similar among treatments.

Conclusions

The project has benefited the consultants and co-operating growers directly involved in the trials by allowing on-hands experience with the novel products, Bloomtime and Blightban C9-1. In this regard, the approach of using on-farm demonstrations has proven to be successful. The results were also communicated to the growers by means of extension activities, for example presentations at meetings and publications. As growers become more familiar with these products, it is expected that they will be more confident in using such biopesticides within an integrated pest management program for apples.

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