Scale are feeding insects that uptake nutrients and water out of tree parts using sucking mouthparts similar to mosquitos. There are many different scale that affect trees in Minnesota. We will go over some of the common scale pests and how to treat for these insects.
In the picture to the right is a magnolia with magnolia scale. This pest feeds primarily on the trunk and twigs of its host. The insects start as small nymphs and grow to the adult size, as seen in the image. There are some common signs a magnolia might have scale, before you see the actual insect. One sign can be bees or flies commonly flying around a magnolia that is not in bloom. The swarms often don't seem to make any sense. The bees are attracted to the excreting honeydew coming from the scale. Another common sight is the bark starts to look black and sooty. This is often the effect of magnolia scale feeding from the previous year.
Cottony maple scale
Maple scale can often be found by buds of maple trees. These insects often do not look like the picture on the right side, as this is a picture of a puffed out female scale. This insect can blend into the branch and look like little bumps on the tree. They feed from the twigs of the tree sucking out essential nutrients and water. This kinds of insect can cause decline in trees with other stressing factors, but rarely is fatal.
The two insects outlined above are classified as heavy armored scales. They tend to be very difficult to control via direct spray applications. These pests are usually controlled with a systemic method such as trunk injections or base drenches.
Pine needle scale
This pest is not very common in pine trees, and only affects longer needle pine trees. Unlike the other two scale, this scale affects the needles or "food factories" of the tree. They feed in a similar way to spider mites. Pine needle scale are often found near the bottom of the tree rather than spread completely throughout like magnolia scale. The picture to the right shows a mass infestation of this insect. These are soft scale and can be controlled with spray applications or with a systemic approach.
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