LACK OF REDUCTION OF FIRE BLIGHT INCIDENCE USING NATURAL PRODUCTS WHICH INHIBIT ERWINIA AMYLOVORA IN VITRO

The ability of three compounds used in apiculture for control of bee diseases to inhibit the growth of Erwinia amylovora and reduce fire blight incidence was assessed in the laboratory and in the field.
These three compounds, lactic acid, formic acid and oxalic acid, inhibited the growth of E. amylovora on plates at concentrations ranging from 3 to 7.5%. They were also able to reduce populations of E. amylovora on quince flowers.
These compounds modified the pH of the growth medium, as well as the pH of the stigmatic surface of apple flowers.
This modification of the pH is believed to be the cause of the inhibition of the pathogen on plates and on stigmas.
The most effective of these acids in reducing population of E. amylovora on quince flowers was formic acid, which was also the acid which modified the pH of apple stigmas the least.
These three compounds proved to be phytotoxic, burning apple flowers.
When the concentration of formic acid was lowered to avoid phytotoxicity, no reduction of the incidence of fire blight was observed.

X International Workshop on Fire Blight

J.L. Vanneste, G. Fischer, A. Spornberger, H.C. Pechhacker, F. Berger

honey bees, lactic acid, formic acid, oxalic acid, Quince

https://doi.org/10.17660/ActaHortic.2006.704.52