There are a wide variety of Scale insects in our area that affect a multitude of trees and shrubs. They will all severely weaken and eventually kill affected trees and shrubs as their populations accelerate. Scales are exceptional at ‘over-wintering’ and resume feeding and multiplying the following year, and they do so at an alarming rate.
The following four Scale varieties are by far the most common and highly damaging Scale insects in our area:
Euonymus Scale and Pine Needle Scale appears as tiny whitish spots on the leaves and stems. The shrub or tree may appear totally white as if covered by snow in heavier infestations. The base of the stems may also have brownish oyster shell shaped bumps. As the Scale continues to multiply the leaves begin to fall and branches begin to die. Even though the plant may look severely damaged, a lot of it may recover in the months and years to come after treatment begins. We always recommend that clients not trim away branches that appear dead until after the second season of treatment, as a lot of what appears to be dead might not be.
Cottony Maple Scale first appears as tiny hard shells on the bottoms of tree branches. They are somewhat like a small ladybug shell both in size and shape, but the color of this Scale’s shell is medium to dark brown. They attack mostly Maples (especially Silver Maple), but they also attack Honey Locust and several other trees. These shells begin to open around July, and they resemble ‘popped popcorn’ all over the undersides of leaves, stems and branches.
Magnolia Scale first appears as shiny brown crusty bumps. As summer progresses, the Scale matures into powdery white and grayish bumps. This Scale insect doesn’t begin to emerge until late September and into October. The main thing that homeowners notice throughout the entire summer with both Cottony Maple and Magnolia Scale is the constant sap dripping all over their cars, decks, patio furniture, swing sets and children's toys. Even the grass beneath is sticky to walk on. This is caused by the insects feeding from within their pods. As they pierce the bark with their mouthparts and feed, they excrete a sticky substance called Honeydew, which turns black, as a substance called 'sooty mold fungus' forms.
All Scale insects are difficult to control. Many of the insecticides from years past (which are still available) do not work any longer, as Scale insects are masters at developing tolerances and immunities to repeatedly used insecticides. Resulting from extensive research and trials, Tree Green's insect management program consists of rotating insecticides and properly timed spray applications, which is the key to superior control. We have found that trunk injections or soil drenching applications do not work well.
The timing of applications and products used vary for each type of Scale. Rest assured that Tree Green’s 40+ years of experience in this industry, and extensive experience with different Scales, will result in clearing up this situation!
It is important to note that even after a treatment or two, the shell of the Scale insect may still be present on the tree or shrub for a period of time. It could be up to one year on the Maples and Magnolias and possibly 2 years on the Euonymus. This does not mean that the insect is still actively damaging the tree or shrub! The Scale shells just need time to begin decomposing and ‘slough off’ the stems and branches naturally.