The present invention provides an insecticidal oil-based formulation, which comprises a petroleum hydrocarbon oil, a nonionic surfactant suitable for emulsifying the petroleum hydrocarbon oil, a desiccating agent and an insecticidal filamentous fungus; and a method for controlling insect pests, which comprises applying said formulation to an insect pest, a habitat of the insect pest or a plant vulnerable to the insect pest; and the like.