Resident ladybugs and other predators can substantially reduce aphid populations. Take care to protect and encourage these predators. Also limit damage by removing aphids with a stream of water from a garden hose or by smashing them. Insecticidal soap, malathion, and diazinon will control aphids. Cabbage maggot These underground larvae inflict damage on cabbage family varieties and radishes.
Flies lay eggs on plant stems or near the ground level.
The eggs hatch into maggots. Destroying crop refuse and trash in the fall will help eliminate overwintering sites for these pests. Controlling wild mustard around the garden will help reduce cabbage maggot fly populations. Covering plants with floating row covers helps keep flies from laying eggs on or near plants. Surrounding stems with paper collars might help deter downward movement of maggots that do hatch on the stems.