DECREASE OF SUGAR CONTENT OF BACTERIALLY INFECTED APRICOT BRANCHES IN RELATION TO FREEZING INJURY

One type of apoplexy disease syndrome is the dieback and canker of apricots which is the most serious disease in the majority of apricot growing countries.
Earlier studies have shown that in addition to Cytospora cincta mainly Pseudomonas syringae is responsable for the apoplexy disease of stone fruit trees in Middle-Europe.

It is well known, that the bacterial cankers and dieback develop only if bacterial infection occurs after leaf drop and during the winter months (Klement et al., 1974). Numerous statistical surveys proved that the bacterial dieback is characteristically more severe after cold winters.
Fron this observation many farmers have come to the conclusion that one of the most important cause of apricot apoplexy is the winter frost.

In order to find out the role of the winter injury experiments were carried out under field and laboratory conditions.
Artificial inoculation with Pseudomonas syringae were done in a warmer (at the Adriatic coast) as well as in a colder climatic zone (near the Hungarian border) in Yugoslavia (Klement, Rozsnyay and Arsenievic, 1974). Where the winter temperature was around 0°C, phloem and cambium necrosis did not occur.
However, in the northern part of Yugoslavia, where the temperature dropped below —15°C, cankers at the inoculation site were extremely long, 24 to 92 cm.
Consequently, the extend of the bacterial cankers depended on the strength of winter frost, but without bacterial infection phloem necrosis does not develop.
This field experiments were repeated in laboratory, too.

VII Symposium on Apricot Culture and Decline

Z. KLEMENT, A. BÁLÓ, G. PRILESZKY, Z. ROZSNYAY

https://doi.org/10.17660/ActaHortic.1983.121.58