This paper presents the results obtainded in monitoring three apple-tree cultivars Voinea, Jonathan and Golden Delicious, from experimental polygon of of S.C. FRUCTEX S.A. from Bacau affected by apple’s proliferation (Mycoplasma sp). As a results of numerous observations concerning the evolution of apple’s phenophases; production (t/ha); the quality of fruits; the amount of affected trees by apple’s proliferation, no species have been indentified to be very resistent or resistent on proliferation, the amount of attack having values over 1%.