BIOLOGICAL-CONTROL OF CROWN GALL IN CHERRY ROOTSTOCK PROPAGATION

English isolates of Agrobacterium tumefaciens from cherry were sensitive to the bacteriocin produced by A. radiobacter strain 84 in vitro, and simultaneous inoculation of the 2 organisms into tomato stems or cherry leaf scars completely inhibited the gall formation that occurred in the absence of strain 84. However, attempts to achieve biological control of crown gall of cherry in the field were successful only when the antagonist was applied as a preplanting treatment to cuttings. Disease on infected cherry layers was not reduced even after 3 sprays of the antagonist. A. radiobacter strain 84 was also ineffective as a preplanting dip, or both preplanting and post-harvest dips for symptomless, but latently infected, rootstocks harvested from an infected layer bed.