Fire blight of pears in Israel: Infection, prevalence, intensity and efficacy of management actions

The Pear production area in Israel is 1500 ha, most of which (ca 1200 ha) i s located in the northern part of the country. Fire blight (caused by the b acterium Erwinia amylovora (Burrill) Winslow et al.) was first observed in Israel in that region (in 1985) and the disease has prevailed there since t hen. In a comprehensive survey conducted in Israel in 1996-1999, data were collected and observations were made yearly in one-third to one-half of the pear production area. The aim was to document the prevalence and intensity of fire blight in commercial orchards and to use the data to evaluate the efficacy of management measures employed for its suppression, Regionwise, a severe fire blight epidemic developed in 1996, moderate epidemics develope d in 1998 and 1999, and a mild epidemic developed in 1997. The intensity of fire blight in the preceding season in a specific orchard was more influen tial on current season severity in a season with a mild epidemic than in a season with a moderate epidemic. Analysis of disease onset records and weat her data revealed that only a few (1-3) infection episodes occurred in indi vidual orchards each year. Comparison of fire blight intensity in orchard-p lots treated before green tip with copper hydroxide with nontreated plots r evealed that the treatment had no effect on disease intensity during bloom. The efficacy of bactericide sprays applied during bloom was not related to the number of sprays applied but to the timing of spraying. Adequate contr ol was achieved in orchard-plots sprayed soon before or after the occurrenc e of infection episodes.