Survey on Erwinia amylovora in pear orchards in Israel
In Israel, pear trees are grown on approximately 1500 ha, mainly in the northern part of the country (1200 ha) in western and upper Galilee, and Hula valley. Erwinia amylovora (EPPO A2 quarantine pest) was first reported in Israel, in 1985, in the northern part. Within 2 years, the disease spread to all pear-producing regions of Israel. During the 10 years that followed the introduction of the disease, foci were scattered and the intensity of the disease remained mild on average. Nevertheless, in some areas the disease was severe, leading to yield losses, tree mortality and uprooting of entire orchards. Severe outbreaks were then respectively observed in the Sharon production area (75% pear orchards had to be destroyed) in 1995, and in the northern part of Israel, in 1996. This has triggered a survey on E. amylovora in pear orchards from 1996 to 1999. The aim was to determine the extent and intensity of the disease, and to evaluate the efficacy of control methods. Information was collected on: extent and severity of the disease, exact location of orchards, phenology of the crops, climatic data, treatments applied (copper, bactericides). The identity of the pathogen was checked in several instances, and the presence of E. amylovora was always confirmed. On average, the survey showed that the disease was severe in 1996, moderate in 1998 and 1999, and mild in 1997. This general trend did not necessarily reflect the situation in individual orchards, as severe outbreaks could be seen during mild or moderate years and vice versa. Results also showed that, in a given orchard, the disease intensity observed during the previous season could provide a good estimation of the probability of disease incidence during the following season in years with mild epidemics (but not in years with moderate epidemics, as a higher pressure of the disease probably favours spread from one orchard to another). It was also found that copper treatments applied before bloom in order to reduce the initial inoculum were not efficient, and therefore they are no longer recommended to growers. Concerning the efficacy of bactericide treatments, it was showed that the key element was the correct timing of the applications and not the number of applications. These treatments must be applied shortly before or after the occurrence of infection periods.
Sources
Shtienberg, D.; Oppenheim, D.; Herzog, Z.; Zilberstaine, M.; Kritzman, G. (2000) Fire blight of pears in Israel: infection, prevalence, intensity and efficacy of management actions.
Phytoparasitica, 28(4), 361-374.