On the kinds of rat and its distribution,occurrence and damage dynamics in agriculture fields of Tonglu county

Monitoring monthly of rodent infestation in farmland for twenty-first years in Tonglu County and a census data of rodent infestation in 2005 were carried out.The results showed that the Striped Field Mouse was dominant species in farmland rodents,secondly was Rattus norvegicus,but the proportion of the rodent population in all farmland rats was obviously raised.R.norvegicus and Mus musculus were dominant species in farmhouse rodents.There were two obvious peaks of rodent population density in farmland among different years,which was from November to December and from June to July,respectively.Similarly,there were also two peaks of rodent density in farmhouse,which was from November to March and August,respectively.In recent years,rodent density in farmland had obviously decreased and kept a lower density,but rodent density in farmhouse was high and widely distributed.Inter-annual change of rodent density in farmland was in good agreement with the dynamics of loss rate damaged by rodents of main grain crops.According to occurrence and distribution characteristic of rodent in farmland,key areas and key works of deratization were put forwarded.