Adelgids affect conifers and not leaf bearing species. Adelgids are aphid like insects that suck the sap from conifers. Often covered in a white waxy material, some also cause galling on host plants. They feed on conifers and can have complex lifecycles including more than one host.
Control
Adelgids can be difficult to control with insecticides as they are protected their waxy secretions and there are no controls for the gall forming stages. Control solutions are the same as those listed above for mealybugs.
Species often found in gardens are below and are also clickable links for further information:-
Further information can be found under the separate headings above