At a Glance
- Fire blight can severely damage orchard health, productivity, and long-term viability.
- Infected wood, shoots, and fruit become blackened and die, reducing yield.
- Active infections can spread rapidly within and between orchard blocks.
- The disease overwinters in tree cankers and re-infects new tissue in spring.
- Bloom is the highest-risk period for fire blight infection.
- The BC DAS system helps growers assess risk and time control measures effectively.
Why Is Fire Blight a Problem?
Fire blight can have a major impact on orchard health and productivity. Infected wood, developing tissues, and fruit often become shrunken and blackened, losing the ability to produce new growth. Affected limbs not only reduce current production but also act as ongoing sources of infection throughout the growing season.
Because infections can spread within a tree and across an orchard block, fire blight has the potential to compromise large areas if not managed carefully. Reduced fruit production and continued disease pressure can significantly limit pack‑out returns and long‑term orchard performance.
Where Does Fire Blight Come From?
Fire blight is an orchard disease present in the Okanagan and is caused by the bacterium Erwinia amylovora. It affects apple and pear trees, among other hosts. The bacteria overwinter in previously formed cankers on infected trees. In spring, these cankers begin to ooze bacteria, which can re-infect new, developing tissue.
Bloom is the most dangerous period for fire blight infection. Bacteria can be transferred from blossom to blossom by pollinators, people working in the orchard, and orchard equipment. When bacteria land on an open flower, they grow in the nectar and cause a blossom infection. These early infections often go unnoticed and may not show visible symptoms until one to four weeks after bloom, leading to secondary infections later in the season.
How the BC DAS System Helps
The BC DAS system helps growers stay informed about the current risk of fire blight infection based on their specific orchard location. By using information on leaf wetness, wetness duration, and precipitation events from selected local weather stations, the system identifies periods when fire blight risk is elevated.
To improve accuracy, growers are encouraged to select the infection history that best represents each orchard block, indicating whether fire blight has occurred previously, currently, or only rarely. The system integrates this information with weather data—including temperature, TRV, and short-term forecasts—to determine when conditions are most favourable for infection and when control measures may be warranted.
Support for Fire Blight Management
The BC DAS Fire Blight model also includes access to control information through the DAS Spray Guide. When orchard conditions indicate a need for control, growers can review spray options, rates, and timing recommendations. The guide allows selection of products registered for conventional or organic use, helping growers plan appropriate coverage.
By following the BC DAS Fire Blight model, growers have timely access to relevant information and tools to support decision making and reduce the risk of fire blight spreading within their orchards. For more information, check out the Tree Fruit Production Guide.
Learn More (Video)
Interested in learning more? Check out the BC DAS Fire Blight model video on YouTube to see how field knowledge and observations connect with the online DAS system.