Fire blight is a destructive bacterial disease of apples and pears; which destroys blossoms, shoots, limbs, and sometimes the whole tree. The disease occurs worldwide in all moderate to warm apple growing areas. Outbreaks are typically very sporadical, causing severe losses in some orchards in some years while no damage occurrs in others. This occurrence is attributed to
a) differences in the availability of overwintering inoculum
b) the specific conditions for infection
c) variations in specific local weather conditions and
d) the stage of development of the cultivars.
The destructive potential and sporadic nature of fire blight, along with the fact that epidemics often develop in several different phases, makes this disease difficult and costly to control (P.W. Steiner, T. van der Zwet, and A. R. Biggs).
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