I pulled all my lettuce out tonight, because they were too infested with aphids to keep. I tried blasting them with the hose several times, but I think the infestation was just too bad to get them all off. I still have plenty of arugula, so I have greens to keep me happy :) I was wondering if the aphids stay in the soil and will infest the next plants that I put there. I was going to plant some eggplant there tonight, but I looked at the soil and there were a few aphids on the soil. Later, they seemed to be gone, but I didn't want to take the chance of a re-infestation. There was 1 ladybug hanging around, and some little yellowish/orange eggs on the back of one of the lettuce leaves. I was hoping these were ladybug eggs, so I left the leaf on the ground. Should I treat the area with anything before re-planting??

Thanks!