Organic Insecticide

I applied an insecticide made of hot pepper, natural soap, garlic, lemon peel, and water to a variety of plants that were being damaged by aphids and other pests. However, a week later, there is no difference between the control and treatment group. I think the problem is that the aphids need to be sprayed directly, and when I sprayed the plants, there may not have actually been any bugs on them at the time. Going forward, if I spot a colony of aphids, I will be sure to attack.