EFFECT OF BORDEAUX MIXTURE – OIL SPRAYS ON FIRE BLIGHT CANKERS

The effect of concentrated sprays of Bordeaux mixture plus spray oil on the recovery of Erwinia amylovora from fire blight cankers was studied during two growing seasons.
Cankers on pear trees in western New York State were selected early in the spring and single sprays were applied at the bud burst stage of development.
By swabbing intact canker surfaces, the fire blight bacterium was recovered from significantly more unsprayed cankers than sprayed cankers.
Recovery of fire blight inoculum from sprayed cankers was reduced markedly through the petal fall stage of development; later, more sprayed cankers yielded the pathogen.
A greater percentage of unsprayed cankers on the Buerré Bosc cultivar released inoculum than comparable cankers on the Bartlett cultivar.
These studies indicate that Bordeaux mixture plus oil reduces fire blight by reducing the production of primary inoculum by overwintering cankers.

Symposium on Fire Blight

Steven V. Beer

https://doi.org/10.17660/ActaHortic.1978.86.13