Abstract: Managed honey bees (Apis mellifera) are the most economically valuable pollinators offruit crops worldwide. However, bee populations suffered significant declines in recent years, andthe extensive use of crop protection products is considered by many beekeepers to be at leastpartially responsible for this. With the ultimate goal to provide new insights for the development ofnovel objective methodologies to detect and quantify sublethal effects of pesticides, we haveconducted a research project in which a multidimensional approach was followed to identify andevaluate such side effects. During the 2008 season, we intensively monitored a set of bee hives thatwere contaminated with sublethal doses of commonly used crop protection agents (fenoxycarb,imidacloprid and indoxacarb). Although no short-term toxic effects were observed, as it could beexpected by using sublethal intoxications, significant differences for several colony vitalityparameters were obtained a couple of weeks after treatment. Based on the outcomes of experimentscarried out simultaneously to test the foraging behaviour, we postulate that these effects are at leastpartially caused by the aberrant onset of foraging, i.e. abnormal timing of bees’ shift from in-hivenursing activities to outside food gathering activities.