Aphids are soft-bodied insects that use their piercing sucking mouthparts to feed on plant sap. They usually occur in colonies on the undersides of tender terminal growth. Heavily infested leaves can wilt or turn yellow because of excessive sap removal. While the plant may look bad, aphid feeding generally will not seriously harm healthy, established trees and shrubs. It often takes more than one treatment to control aphids. If you have an aphid infestation, BC can help!