Development and evaluation of a decision support system for management of fire blight in pears

Severe epidemics of fire blight (caused by Erwinia amylovara) have developed since 1996 in the main pear production areas in Israel, leading to death of trees and uprooting of orchards. Consequently, a national R&D project was initiated in 1997 with the objectives of testing the activity of various bactericides against E, amilovora and of developing a tool for optimal timing of sprays. Eleven experiments were conducted in 1997 and nine in 1998 in commercial orchards located in most pears growing areas of the country. Natural epidemics developed in five of the experiments; in addition, four experiments were artificially inoculated with the bacterium. Of all bactericides tested, only oxolinic acid (Starner, Sumitomo Chemicals, Japan), applied at a rate of 0.15%, significantly suppressed the disease (by 75.1+/-3.9%) in all experiments. A rate of 0.1% was not effective when a severe epidemic had developed. A local decision support system named Fire Blight Control Advisory (FBCA) was developed. The following parameters are considered and integrated into FBCA: the host (tree-age, crop developmental stage, degree of shoot growth); the pathogen (previous and current disease intensity and pathogen activity in the orchard and in adjacent orchards); the environment (temperature, duration of wetness and rain; both past and forecast); and grower's actions (sanitation, bactericide spraying). Disease severity in plots treated according to FBCA differed significantly from that in untreated plots in all experiments, and disease suppression (78.2+/-4.1% of control) did not differ significantly from that in a predetermined 3-5-day spraying treatment. FBCA will be further evaluated during 1999 in replicated experiments and it will also be operated experimentally by commercial growers.