The weather conditions during the last years were favorable to the growth of the populations of Microtus arvalis in Sibiu County. This pest rodent sheltered within all the agricultural cultures as well as in pastures, hayfields, slopes, the road sides. Its presence grew alarmingly in orchards, too. In order to put into practice correctly the control and warning measures there was necessary to establish the density of this pest. So, in order to determine the number of colonies as well as the percentage of attacked trees there were investigated 929 hectares of orchards. Researches upon the species Microtus arvalis were done by Săvescu, 1960; Manolache and Boguleanu, 1967; Tuţă, 1980; Teodorescu and coworkers, 2003; Paşol and coworkers, 2007, and so on. The investigations were done during 3 rd September 2009 – 15 th September 2009 in 7 orchard firms in the localities Viile Sibiului, Cisnădie, Şura Mare/Slimnic, Şura Mare (Agnita), Ruja, Miercurea Sibiului (Sibiu County). There was checked the surface of 929 hectares of orchards and there were identified the trees that were attacked by the rodent on the parcel of tree species. In order to determine the number of colonies as well as the percentage of the trees attacked by the mice there done soundings in zigzag as well as on the diagonal of the parcel. In the parcels where the trees were sustained by a sustaining system the sounding was done alongside the tree rows. In the same time there was investigated the dependence of the population of Microtus arvalis on the values of environment factors during 2009. There is considered that the results of the investigations are of a special economic importance, these being used afterwards in appreciating the best moment to put into practice the control and warning measures against this rodent. In the same time was brought to present the data regarding the orchards patrimony in Sibiu County.

biological reserve; Microtus arvalis Pall

Presentation: oral