OVERWINTERING OF ERWINIA AMYLOVORA: SOURCES OF INOCULUM IN SPRING

ISHS Acta Horticulturae 117: II Symposium on Fireblight

OVERWINTERING OF ERWINIA AMYLOVORA: SOURCES OF INOCULUM IN SPRING

Author:

J.P. Paulin

Abstract:
Sources of fireblight inoculum in spring have been reviewed by Schroth et al (1974), and Beer (1979). It seems clear that bacteria available for blossom infections originate mainly from hold over cankers, although Erwinia amylovora can be detected on other parts of the trees as well.

When eradication of fireblight is planned from a newly infected orchard in a recently contaminated area, it is essential to know:

if the bacteria are present on diseased trees only,
whether contamination of healthy host plants in the vicinity of infected ones can occur
if the bacteria are able to survice on weeds, in soil etc. from the autumn until the next spring.

E. amylovora apparently can maintain itself in cankers (Beer and Norelli, 1977), twigs (Keil and Van der Zwet, 1972, Aldwinckle and Preczewsky, 1976), buds (Bonn, 1978), fruits (Goodman, 1954) and soil (Ark, 1932).

Successful detection of the bacterium in host tissue or soil may depend on techniques used in the detection of the bacterium. Climatic or other local conditions may have an influence on the degree and duration of plant tissue or soil to remain contaminated.

Therefore it was tried to detect Erwinia amylovora, by means of different techniques, on different materials (plant material and non plant material, host and non host plants), in the South West of France, where fireblight is increasingly important (Paulin and Lachaud, 1978).

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