STUDIES ON INTERRELATIONS BETWEEN STEM PITTING PATHOGENS FROM APPLE, PEAR, CHERRY, AND PEACH

About 73% of apple varieties, approximately 50% of apple rootstocks, and 50% of cherry varieties are infected with stem pitting. Not more than 1% of diseased trees can be found in pear and peach orchards.

We could show stem pitting virus infection of apple by using Virginia crab as indicator. Stem pitting symptoms were determined also on wild species of genus Malus, for instance M. micromalus and M. baccata var. oblongata, and on the varieties Pervenetz Samarkanda and Golden Nolik, both these cultivars were received by hybridization with M. syversii

On cherries stem pitting infection is sometimes accompanied by growth suppression, dying of branches and tree decline, but in some cases the diseased trees show normal growth. The following varieties proved to be infected by stem pitting: Schpanka kurskaya, Krasa Severa (Northern Beauty), Griot Ostheimskiy (Ostheimer Weichsel), Anadolskaya, Jubileynaya Mitchurina, Samsonovka, Shirpotreb tchernaya (black), Podbelskaya, May Duke, Botsenskaya, and Seyanetz Avdeeva (Avdeev's seedling); all these cultivars are grown on Prunusmahaieb rootstocks.

Among peach varieties nearly all trees of Golden Jubilee are infected by stem pitting. The diseased trees show suppressed growth, a flattened crown, they are almost without fruit, the bark is thick and bright-yellow. These symptoms are similar to those described by American authors (Barrat et al., 1968; Stouffer, Smith, 1971).

On pears stem pitting is in some but not in all cases accompanied by an early reddening of leaves.

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