With recent rain and higher temperatures in the Pacific Northwest, conditions are ripe for fire blight disease development in your apple and pear orchards.

Fire blight overwinters as cankers on trees in infected orchards, and secretes bacterial residue that can be spread throughout the area. As temperatures rise, bacteria that survived the winter begin to ooze from cankers, attracting insects that use the ooze as a food source. Now carrying the bacterium, insects feed on the nectar of flowers, transmitting the pathogen. As the growing season progresses, infected flowers, twigs and leaves will blacken and appear scorched.

Syngenta Agronomy Service Manager Chris Clemens shares his thoughts about rising incidents of fire blight in the Pacific Northwest.

Pome blocks of highly susceptible varieties on highly susceptible rootstocks are experiencing more frequent and more damaging infections of fire blight across the Pacific Northwest. To manage this disease, we suggest:

• Minimize early-season irrigation during periods of high humidity.
• Monitor trees 2 weeks after full bloom for visible infection.
• Control cover crop and weed growth.
• Thin out blossoms.
• Use prediction systems to monitor disease presence in your area:
  • PNW Pest Alert Network
  • WSU-Tree Fruit Decision Aid System

If these conditions persist, we recommend implementing a management program that includes Actigard® plant activator. Actigard triggers the tree’s natural defense system, much like a vaccine. When used in rotation with antibiotics, Actigard delivers enhanced protection from fire blight.

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