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11 Questions About Using “Bloomtime” and “BlightBan” to Suppress Fire Blight

Q: What are Bloomtime and BlightBan?

A: Bloomtime and BlightBan are the product names for two different strains of the non-pathogenic bacteria Pantoea agglomerans. Bloomtime is strain E325 and BlightBan is strain C9-1.

Q: How do these products work against fire blight?

A: Both products work to suppress fire blight. Pantoea agglomerans is a bacteria antagonistic to Erwinia amylovora, the bacteria that causes fire blight. P. agglomerans colonizes the same areas of the blossoms and utilizes the same nutrients as the fire blight bacteria, but P. agglomerans does not cause any damage or plant disease. These biological control products do not work well if the fire blight pathogen has already colonized the blossoms.

Q: Can I use Bloomtime or Blight Ban instead of streptomycin?

A: No. These products only suppress fire blight; “suppression” indicates around 60% control without additional measures. These products should be used in a management strategy that includes monitoring, predictive models, cultural controls, and the use of streptomycin.

Q: Are these products registered for apples or pears?

A: Both products are registered for pears and apples.

Q: What are the advantages of using P. agglomerans?

A: Suppressing the fire blight bacteria can have major benefits to lowering the incidence of the disease. Lower numbers of colonizing fire blight bacteria also mean that streptomycin applications can be more effective and there may be years when less streptomycin can be applied. Fewer applications of streptomycin is one method to help reduce the risk of development of streptomycin-resistant fire blight bacteria.

Q: When should P. agglomerans be applied?

A: The labels of both products say that the first application should be made around 15 – 20% bloom with a second application at full bloom. Blooms must be open for P. agglomerans to enter and colonize, thereby out-competing the fire blight bacteria. It is very important to spray these products when blooms are open and before the fire blight bacteria have a chance to colonize the blossoms. Predictive models like Cougar Blight and MaryBlyt are necessary to predict fire blight infection risk periods and enable growers to target the best time to spray.

Q: How many times can I apply P. agglomerans?

A: At present, BlightBan is allowed 3 applications per year but Bloomtime is labeled for only 2 applications. That may change in time.

Q: Are there any precautions about using P. agglomerans?

A: Yes. Besides the normal safety precautions on the label, it is important to remember that copper is toxic to P. agglomerans, so should be avoided leading up to applications of these products. Copper applications during tree dormancy are not likely to affect the performance of Bloomtime or BlightBan. Sulfur is probably fine with these products and no other incompatibilities are known at present. More research into the compatibility of these products is required. At this time it is not advisable to tank mix these products with any other pesticide.

Q: Are there any precautions with storing these products?

A: Yes, biological products are not like chemical pesticides and certain precautions are necessary for storage. These biological products contain living organisms and must be kept frozen in their original container until application. They also have a short shelf life of 5.5 months and therefore unused product cannot be stored for use the following season.

Q: How important is coverage?

A: As with other conventional products, good coverage is important to ensure that the products get inside the bloom. These products are not systemic nor do they actively move into blooms. Applying these products with 1000-2000 liters of water/ha is very important to obtain good coverage.

Q: Where can I buy Bloomtime or BlightBan for next season?

A: We do not yet know who will be distributing these new additions to the fire blight arsenal. For this coming season though, they will likely be in short supply as the companies move slowly into the market and gain field experience in various areas.