INCIDENCE OF SOME GRAFT-TRANSMISSIBLE DISEASES IN SOUTH AFRICAN POME FRUIT NURSERY MATERIAL

Randomly selected apple and pear nursery sources, propagated from visually inspected mother trees onto seedling rootstock, demostrated a high incidence of latent virus infections. On apple multiple infection with apple chlorotic leaf spot, apple stem grooving, apple flat limb, Spy 227 epinasty & decline, apple rubbery wood, platy-carpa scaly bark, platycarpa dwarf and apple mosaic were common. In pear multiple infections with pear ring pattern, pear vein yellows, apple rubbery wood and Spy 227 epinasty & decline were common. Pear rough bark and quince stunt were also detected. the erratic performance of some indicators suggests masking of disease symptoms under elevated field temperatures.