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Fireblight (Erwinia amylovora)

Wednesday May 20, 2020

Blackened leaves and tissue caused by Fireblight
Fireblight infection with characteristic dead wood and leaves at terminal tips

Fireblight (Erwinia amylovora)

Why is it a problem?
Fireblight infections can greatly affect the health of your orchard, causing wood, developing tissues and fruit to become shrunken and blackened, rendering them unable to produce new tissue. Compromised limbs not only reduce the productivity of your orchard, but also serve as sources for continual and persistent infections of this disease throughout the growing season, with the potential to contaminate an entire orchard block. Reduced fruit production and potential for further infection of orchard crops should be a concern for growers, as both can greatly limit the amount of return from the packinghouse to the grower.  
 
Where does Fireblight come from?
Fireblight is an orchard disease present in the Okanagan which is caused by the bacterium Erwinia amylovora, and effects both apple and pear trees, among others. Fireblight bacteria overwinters in previously formed cankers present on the trees, which will ooze bacterial spores that have the potential to re-infect developing tissues. Bloom time is when Fireblight infections are most dangerous, as Fireblight bacteria from oozing cankers can easily be transferred from blossom to blossom by pollinators, by humans doing tasks in the orchard, and by use of orchard tools. Spores landing on the open flower will grow on the nectar within the flower itself, causing a blossom infection which can lead to secondary infections later in the season. Many times infections occurring during this bloom time will only reveal symptoms 1-4 weeks after the blossom infection.  
 
How the BC DAS system can help: Keeping you Informed + Equipped
The BC Das system allows growers to be informed about the current risk of Fireblight infections in the growers' specific geographic location. Using information on leaf wetness and duration, as well as wetness and precipitation events from the local weather stations that the grower has selected as being reflective for their orchard, the BC DAS system provides the grower with up to date information regarding potential risks for Fireblight infection. In order for the BC DAS system to be most accurate, the grower must select the infection history which is representative for their particular block, and input whether an Fireblight has occurred previously, currently or seldom in their specific area. The combination of pulled weather information such as TRV, maximum and minimum temperatures, and the upcoming forecast will prompt the system to send out notifications to alert growers for when control measures are best suited for use, and give details on what other factors growers should consider when evaluating a risk.  
 
In addition, the BC Das system has control measures incorporated into the Fireblight model webpage. What this means is, when orchard conditions reflect the need for Fireblight control, the grower is then supplied with the tools needed to ensure coverage against this disease. The DAS Spray Guide offers different spray options, rates and timings, allowing growers to plan their sprays for coverage, as well as allowing the grower to select for product options currently registered for either conventional or organic use. By following along on the BC DAS model, the grower will have timely information and knowledge of the tools currently available to protect against Fireblight populations in their orchard.  
 
Still interested in finding out more? Check out our BC DAS Fireblight model video on YouTube to connect horticultural knowledge from the field with the online DAS program: