Dark Brown or Black Shells on Oleander May Be Scale Insects

Q. I have a serious infestation of hard shelled black insects on my oleanders. I have a tree-like hedge of oleanders on both sides of my home. One of the oleanders is heavily infested but the problem is spreading rapidly to all the others.
When I discovered the problem this weekend the oleander was black with thick black shelled insects about the size of an apple seed with sticky honeydew dripping down the trunk and stems. My neighbor thought they were black aphids so I power sprayed the oleanders with water and used a soapy water rinse. Unfortunately, the bugs seem to be adhered and need to be picked off. They are not on the leaves but are on the stems and trunks and climb higher than I can reach. I am attaching photos and would appreciate any advice you can give me. Will the 100^o+ weather kill them? I removed the most heavily infested branches but that barely made a dent in the insect population so I wonder if I have to remove the whole oleander tree.

A. This is one of the many scale insects. Scale insects are not terribly common in southern Nevada. They are difficult to control because the insect is living under a protective “shell” it created.

            Because the insect does not move around once it creates its “shell” they don’t attract attention. Frequently they come to our attention because of the sticky sap they excrete is shiny and attracts ants.

            Oftentimes the question becomes how can I control ants, not realizing the ants are there because of other insects like scale and aphids. The ants can move the scale insects around so it is best to control them as well.
            If you don't have very many of them you can treat each scale with alcohol and a cotton swab. But usually there are too many.

            The usual recommendations for controlling scale insects is to either spray a horticultural oil on top of them in early spring to suffocate them or use a conventional insecticidal spray. a conventional insecticide when the insect is no longer protected by its hard outer covering, the scale itself. Never spray an oil when a plant is in bloom. Usually two winter or early spring applications are called for.

One of the many horticultural oils for suffocating insects. Particularly good on soft-bodied insects like aphids, mites and the like but they will also kill beneficial insects so use it where and when it is needed and not indiscriminately.

These insects are not hard to kill when they are not under those shells. The females release young scale insects without the scale (called crawlers) around May. It is at this time the insects are most vulnerable. It is also the time when it starts getting hot and the spraying oils in the heat is not recommended. I have done it very early in the morning with no problems to the trees but you must do it early in the morning.

When in doubt, spray a small area of the plant first and wait 48 hours to see if the plant reacts negatively to it. If it doesn't, go ahead and spray in the summer as well but do it in the cool morning hours right after sunrise.