Image of developing pear fruitlet infected with fire blight
Apples Diseases Pears Pest Management

Fire Blight Infection Risk Continues

Warmer temperatures and rain forecast this week put apple and pear orchards in bloom at risk of fire blight infection

The fire blight prediction maps for apple and pear continue to be updated as more orchards in the earlier regions of the province enter into bloom. High to extreme infection risk is predicted for many regions in the southwest this week with rain in the forecast. Management will be critical during this time particularly if there is active fire blight in your orchard or neighbourhood.

Fire blight prediction maps for apples:

Fire blight prediction maps for pears:

The prediction maps are updated every Monday, Wednesday and Friday until bloom period is over. Check in regularly to get the most accurate risk prediction.

Fire blight bacteria multiply rapidly in a very short period of time when temperatures are above 18⁰C and relative humidity above 90%. Bacteria can be transferred to new blooms by rain, wind or insect. Bees and other pollinators are very active in the orchard right now and can easily spread the bacteria around. Any wetting event, including rain, dew and even your sprayer will wash bacteria into the floral cup and initiate infection.

Frequent protective sprays may be needed if risk remains high as new blossoms are opening daily and will not be protected by sprays made while these blooms were closed. As well, antibiotics degrade rapidly in sunlight so are only active for 2-3 days MAXIMUM. Apply these products as close to a wetting event as possible. For resistance management with antibiotics, rotate between Streptomycin and Kasumin.

If using biological products such as Blossom Protect, Serenade or Double Nickel, these products have a preventative action so apply when risk is coming in the next 3-4 days. Copper and some fungicides are not compatible with certain biologicals. Check the label. 

Ensure adequate water volumes are used and that sprays are deposited into blossoms. Do not use excessive air speed on sprayers as this will propel sprays past the flower targets. For more information on calibrating an airblast sprayer or troubleshooting coverage, refer to Airblast 101 Handbook.

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