INTERNAL MOVEMENT OF ERWINIA AMYLOVORA FROM INFECTION IN THE SCION AND ECONOMIC LOSS ESTIMATES DUE TO THE ROOTSTOCK PHASE OF FIRE BLIGHT OF APPLE

Fire blight can kill dwarf apple trees by girdling susceptible rootstocks or interstems.
Currently in the Northeast United States, most apple trees are being planted on M.9 or M.26 rootstock or on M.9/106 and M.9/111 interstems, which are all very susceptible to fire blight.
We have good evidence for one mode of infection of the rootstocks: by internal movement of bacteria from infections in the scion.
Movement of bacteria to the rootstock occurs rapidly.
Late season fire blight infections of the scion may be particularly hazardous for the health of the rootstock.
In the summer of 1996, there was a severe epidemic of the rootstock phase of fire blight in western New York.
Rootstock and scion infections were mapped in three different orchards in Ontario and Wayne Counties based on symptom development.
At the Geneva orchard, E. amylovora was detected in all samples by plating on semi-selective medium and confirmed by PCR. Incidences of 2 – 47.5% rootstock infection were determined for different cultivar/rootstock combinations depending on location.
Economic losses resulting from 10% rootstock infections in high density apple orchard were estimated at $8,818/ha ($3,571.31/acre)

VIII International Workshop on Fire Blight

M.T. Momol, J.L. Norelli, H.S. Aldwinckle, D.I. Breth

https://doi.org/10.17660/ActaHortic.1999.489.86