Fire Blight Alert

May 13, 2014

The orchards at the UVM Horticulture Research and Education Center are at open cluster to early pink, and some blooms are expected by the end of the week. NEWA fire blight models are predicting high to extreme risk for fire blight in the next four days for all sites in Vermont except the coolest ones where bud development is still at half-inch green. Growers should consider treatment of orchards with open blooms with streptomycin if infection conditions occur. Remember that fire blight infection requires four conditions:

  1. Open blossoms,
  2. A significant population of bacteria,
  3. Wetting events (including spray application),
  4. Sufficient heat units during the infection event.

The Cougarblight model run through NEWA is the best method to assess infection risk in your orchard. If infection is predicted, streptomycin must be applied within 24 hours before or after the event. Strep only works on open blossoms, so blooms that open after treatment must be re-treated if infection conditions remain.

Please refer to the New England Tree Fruit management guide for more information on fire blight management.

Terence Bradshaw, UVM Tree Fruit and Viticulture Specialist

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The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM Grant, and USDA Risk Management Agency Funds.