Bacterial Canker of Sweet Cherry (Prunus avium) in Poland

Abstract

AbstractIn Polish climatic conditions cherry cankers resulting from infection by Pseudomonas morsprunorum continue development in summer, but the rate may be slower than in the period from April to June.However, from the well established, active canker developing under the dwarf shoot of the susceptible variety‘Hedelfińska’in July no P. morsprunorum were isolated. On the other hand, numerous strains of the genus Erwinia were found there which caused a hyper sensitivity reaction (HR) on tobacco leaves. From the cracks on the current‐year cherry shoots, due to fresh infection and from symptomless leaves P. morsprunorum strains were isolated, always accompanied by those of the Erwinia genus in the approximate proportion 1: 1 or 1:2.The strains of Erwinia genus seemed similar to the DC and YC strains isolated by BILLING and BAKER from pear and apple trees infected by fireblight and also to the strains in group III of the bacteria isolated by CROSSE from cherry leaves.In two tests (immediately after isolation and after 4 months of storage) the strains of the Erwinia genus and 3 nonidentified isolates induced HR. At a third test, after 10 months of preservation these strains were HR‐negative in contrast to the P. morsprunorum isolates.The fact that strains of the Erwinia genus inducing HR were isolated in large numbers from active cherry canker where pathogenic bacteria were not detected, may indicate that they play some role in the development of cherry tree canker.