The small insects on your plant are aphids. They are usually minor pests that can temporarily reduce the aesthetic quality of trees and shrubs (and sometimes spread plant viruses) but they are relatively easy to manage. In your case, it looks like you have natural enemies (beneficial insects) that are already working to control the aphids naturally. There are some brown swollen "aphid mummies" present in your photos. These are aphids that have been parasitized by tiny wasps that laid their eggs inside -- and eventually killed them. Since you have beneficial insects at work, there is no need to use an insecticide. You could simply use a strong spray of water from a hose to wash the aphids off. That will be sufficient to disrupt the feeding of the ones that are still alive. 

Christa

Thank you Crista,