Pollinator trees as a potential inoculum sources for fruit decay fungi on apple

Over the recent years it has become common to plant cultivars of crab apple as pollinators at regular distance in the rows of the apple fields. Little or no specific knowledge exist about the susceptibility to diseases of the various crab apple cultivars used for pollination. The fruits are rarely picked or removed, and if still attached to the fruit trees the following growing season, they may thus become potential inoculum sources for fungi causing fruit decay on apple. Crab apple cultivars, ‘Dolgo’, ‘Professor Sprenger’, ‘Kobenza’, ‘Golden Hornet’, and ‘Evereste’, were evaluated as potential inoculum source for fruit decay fungi. These crab apple cultivars were used as pollinizers of apple cultivars grown in NIBIO experimental unit located in Ullensvang area: They were planted adjacent to apple cultivars ‘NA 42-51’, ‘Elan’, and ‘Rubinola’, to act as pollinizers. To better understand if tree infections and mummified fruit could be contributing to apple fruit decay, sampling was conducted on three experimental orchards at NIBIO Ullensvang and Ås stations during the spring to summer growing season of 2017.M-P