Image of developing pear fruitlet infected with fire blight
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Fire Blight Risk Increases Across the Province

Warmer weather and likelihood of dew has increased the risk of blossom blight in regions that will be in bloom over the coming weekend.

The Ontario fire blight risk predictions maps have been updated for the next 7 days. High to extreme infection risk is predicted for some regions over the weekend. Windy days and increasing pollinator activity this week will have moved bacteria to opening blossoms, particularly if fire blight has been an issue in the orchard or neighbourhood.

It is important to note that these risks are based on accumulated temperature over a period of days. At this point in the season, we are still hovering around the temperatures that would really increase risk. Precipitation also seems quite variable with scatter showers across the province. Areas that see more temperature moderation by lake effects may see a lower risk predicted for their region.

While large amounts of rain are not necessarily predicted until end of next week, sporadic showers can occur. Of more significant concern, however, is the development of dew. With the warm days followed by cooler nights, dew can form. This moisture is enough to wash bacteria into the open bloom.

If antibiotic materials are not being used, blossom protection with other materials should be initiated 1-2 days prior to entering a high infection risk period.

Oxidate is a surface sterilant. Do not apply prior to rain.

Continue appropriate protective sprays until the infection risk drops below the HIGH threshold. Streptomycin provides kickback activity if an infection was missed but should be applied within 12 hours after the event.

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