Foggers are commonly used by professional entomologists to kill pests that spread disease or damage crops. Insecticides are distributed into the air using an atomizing nozzle, which creates a fine mist of droplets. This method of pesticide application can be effective for killing flying insects but does not prevent them from dying after exposure, as insects are also exposed when they come into contact with spray droplets. Many types of insecticides have been tested at different concentrations to evaluate their toxicity against various target species and controls. Although some pesticides cause only immediate mortality without causing long-term harm to non-target organisms, other substances that do not immediately kill insect pests, or even those that slow their rate of reproduction, are often more toxic than many chemical insecticides.