When applied in a dispersed way, for example through fumigation or spraying, these chemicals have an effect against a wide range of insect species, some of which may be beneficial to human activities, including crop-pollinators such as bees. In addition, as with many insecticides, application may result in the killing of natural predators or controls along with the pest,[citation needed] risking the possibility of a 'rebound effect' or pest resurgence, where the original target for the treatment returns with equal or even greater voracity.