Leopold Center
U.S. Department of Agriculture



The most important control of fire blight in the orchard is through acheived through vigilant cultural control. This bacteria is sneaky; it will disappear for ten years and reappear as soon as you have grown sure of its eradication.

  • Dormant pruning of all infected branches and shoots, as well as removal of trees that are too damaged to be pruned, is very important. This must be done each winter, without fail.
  • Supplemental nitrogen should be used only when the tree is visibly stressed. New, growing shoots are good targets for infection, and fertilizers can increase the duration of vegetative growth.
  • Stressed trees are more damaged by infections.
  • Copper sprays before green tip may prevent bacteria from residing on buds and bark.
  • Streptomycin sprays every 3 to 5 days during bloom, or as predicited by MaryBlyt, will prevent infections and control recent infections. Antibiotic sprays are not useful in controlling established infections.
  • Antibiotic sprays immediately following a trauma event (storms, hail, & late frost) can be effective.
  • If you have only a few strikes in the orchard, pruning the infected tissue during the growing season can be cost effective. Make cuts well before the infection and only at an internode. Leave four inches of branch remaining before the internode when pruning to allow any potential small cankers to be easily removed during dormancy.

Email: mgleason@iastate.edu Telephone: (515) 294 0579 Address: 312 Bessey Hall, Iowa State University, Ames IA 50011