Outbreaks of fire blight can occur anywhere in New Zealand under the right conditions. World-wide, the disease is found throughout North America and Canada and much of Europe. New Zealand is the only Southern Hemisphere country where it has been recorded. A severe outbreak can lead to loss of flowers and hence no fruit is produced. It can also cause die-back on trees and can potentially wipe out a whole orchard.
Severe infections are rare on mature trees in New Zealand and are more devastating on young trees.
The main problem is that fire blight is used as a quarantine barrier by fire blight-free countries such as Japan and Australia. The two main forms of chemical control are copper, which must be applied prior to green-tip to prevent russeting, and streptomycin for use during the growing season. Streptomycin is an antibiotic bactericide. Frequent use of streptomycin can lead to the development of streptomycin-resistant bacterial strains and subsequent loss of control. Therefore calender spraying of streptomycin during blossom is not acceptable.