Susceptibility of some apple cultivars to scab (Venturia inaequalis (Cooke) Aderh.) in Slovenia

Summary

The susceptibility of 7 apple cultivars to scab was studied in two locations in Slovenia under a minimal spraying programme. Three cultivars with the Vf gene for resistance to apple scab, ‘Prima’, ‘Priscilla’ and ‘OR 54 T 170’, the cvs. ‘Alkmene’, ‘Lord Lambourne’ and ‘Priols Delicious’ showing a low susceptibility to scab in previous tests, and a standard susceptible ‘Golden Delicious B’ were included in the tests. In the trial orchard ‘Pesnica 82’ surrounded by modern intensive and old extensive apple orchards the susceptibility of ‘Alkmene’, ‘Lord Lambourne’ and‘Priols Delicious’ gradually increased from the 4^th to the 8^th year when scab fungicides were used only 2–4 times per year. In the trial orchard’selo 82’, with no sources of scab infection in the vicinity and therefore low infection pressure, these cultivars preserved their high level of resistance. The standard‘Golden Delicious B’ showed high susceptibility in both orchards. Leaves and fruits of the scab resistant cultivars with the Vf gene occasionally showed few scab lesions in the trial orchard‘Pesnica 82’ under extreme infection pressure.