Abstract
The susceptibility of 26 apple cultivars to four bark parasites: Nectria galligena, Pezicula malicorticis, Stereum purpureum and Phytophthora cactorum was investigated. A close correlation was found between indices of susceptibility to the fungi N. galligena, P. malicorticis and S. purpureum and no correlation between the indices of susceptibility to P. cactorum and the three remaining pathogens. Five groups of susceptibility to the complex of bark canker fungi were distinguished, oomprising three or four species of fungi. Highly susceptible cultivars: 'Delikates', 'Melrose', 'Spartan', 'Prima' and 'Slava Pobeditelam'. Rather susceptible cultivars: 'Starkrimson', 'Hibernal', 'Florina', 'Priscilla', 'Priam', 'Macfree' and 'NY 55-158-2'. Moderately susceptible cultivars: 'Macoun', 'Liberty', 'NY 55-140-9', 'Vista Bella', 'Jerseymac' and 'Šampion', Little susceptible cultivars: 'Discovery', 'Empire', 'Fantazja' and 'Primula', But slightly susceptible cultivars: 'Golden Delicious', 'Idared' and 'NY 58-533-1'.