Aphids suck plant juices and coat the leaves with sticky honeydew. Use sprays of malathion or rotenone. The insects can also be dislodged with high pressure water sprays from the garden hose.
Scale infestations are controlled with dormant oil in the spring before plant growth begins. Crawlers are controlled with sprays of Sevin. The preferred method of control involves regular inspection for early detection of the infestation then spraying with dormant oil.