Do I need to change the soil in my pots to avoid aphids coming back?
I grow vegetables in pots in my driveway (live in a condo). Last year I added kale and late in the season got aphids. I generally compost plants and roots and then leave the pots outside over the winter (and a couple in the garage). Then in the spring I mix in some new compost with the old soil before I plant seedlings.
Should I not use the old soil that had the kale in it? Or do anything else to keep them from coming back if their eggs are in the soil?
The difficult to control cabbage aphid, Brevicoryne brassicae (L.), is the bane of brassicas. These little critters are tenacious. Getting rid of the soil could help to reduce the chances of infestations; however, it isn't a silver bullet. If you get rid of the plant debris and skimming off the soil on the top of the container may be just as good. Getting rid of nearby brassica weeds will help. The reality is that you will most likely see them again. Keeping them under control requires getting them before their populations build. Your best defense is aggressive scouting. Take a look at the following links for additional information on this destructive insect.
I hope this is helpful,