Vattensork och åkersork - skadegörare i svensk fruktodling
VattensorkArvicola terrestrisWater voleåkersorkMicrotus agrestisField voleFruktodlingOrchardFruit production
There are two species of voles that cause damage in Swedish fruit production: the water vole (Arvicola terrestris) and the field vole (Microtus agrestis). Both species make the most damage during the winter season. The water vole makes subterranean burrows and cause serious damage by gnawing on the tree roots. The field vole seldom makes burrows and gnaws the bark at the base of the tree trunk. In recent years there have been several reports about increasing vole damage. The main purpose of this thesis was to estimate the size of the damages, to bring knowledge about the biology of the voles and to give examples of control techniques. By visiting fruit growers and by making a telephone survey, data about damage and experiences from growers were collected. The results show that 36 % of the fruit growers in Sweden think that voles are a problem in their orchard. Many growers reported that the outbreak started in the mid 00?s and growers who already had problems say that it is increasing. Orchards with severe damage seemed to be more frequent in Scania and apple was the most affected species. The water vole caused the most severe damage, especially on young trees in modern, high-density orchards. Damage made by the field vole was only common when there was enough snow on the orchard floor. There was no clear connection between soil texture or surrounding landscape and the presence of voles. According to the fruit growers there was no control technique that was good enough to apply on large areas with high density of water voles. There was a great demand for more research and new solutions for the vole problem.