CHEMICAL CONTROL OF ERWINIA AMYLOVORA BURRILL WINSLOW ET AL. IN PEAR ORCHARDS.
A weekly application of streptomycin sulfate at 100 ppm in one orchard did not prevent further infections during the vegetative period. A weekly CGA 78039 treatment was also not sufficient for a real control of the fire blight disease. Weekly applications of Copac E, an ammoniacal coppersulfate formulation, at 0.5% reduced the number of infections seriously but was not able to prevent all infections. Control of the epiphytic flore of Erwinia amylovora on the leaves, by counting the number of Erwinia bacteria under IF-microscope, confirms the reduction in the number of bacteria in the plots treated with Copac E. An experiment was done for the biological control of fire blight using a strain of Erwinia herbicola : a weekly spray of the antagonist was not effective in reducing infections of fire blight in the treated plot. The experience with FSB 8332 and MBR 10995 is still limited, but some results are promising. Good results were obtained in 1983 with MBR 10995.