Greasy surfaces decrease the effectiveness of insecticide applications. Therefore, before treating surfaces eliminate grease and oil by scrubbing with hot, soapy water. Insect growth regulators will take 4 to 6 weeks for a noticeable decrease in the population. But control is longer lasting than other contact insecticides because the cockroaches are no longer able to reproduce once exposed. Expect to see more cockroaches during the day as a result of IGR use. Seeing more cockroaches after IGR use means the treatment is working. A perimeter treatment along the base of the foundation wall, in cracks and crevices, and at points of entry into the home can also help control the larger outdoor cockroaches.