Question
There are now three very old large maples on our block (two regular and one red) that all have some type of infestation. There are no insects visible. All you can see is small white "cotton like" spots on the leaves. The trees are completely covered. The red maple looks like it has snow on the leaves. The top on my tree has had most of the leaves eaten leaving only the middle stem of the leaf. Can you give me any idea what we are up against?

Answer
Sounds like cottony maple scale.

The cottony maple scale, Pulvinaria innumerabilis (Rathvon), is a highly modified insect pest that commonly attacks silver and red maples. The scales are usually first noticed when the females produce an egg sac which appears as a 1/4 to 1/2-inch long ball of cotton. Heavy infestations can result in branches being turned completely white with the egg sacs. Like most scale insects, the nearly mature insects, the adults and the eggs are resistant to pesticides and the anxious tree owner must wait until the correct time for management.

Normally, this scale is a mere curiosity and nuisance. The white egg sacs easily attract attention and the developing scales produce honeydew. Honeydew is the excess water and sugar excreted by many plant sap-feeding insects. Honeydew is commonly mistaken for "plant sap" being dropped on cars, sidewalks and lawn furniture lying under trees. When honeydew collects on leaves and branches, bees, wasps and ants are attracted to the area. If the honeydew is allowed to remain, molds called "sooty fungus" grow on the material, turning the surface a gray-black color.

Occasionally, heavy outbreaks of this scale occur, usually on weakened or stressed trees. These outbreaks can cause the death of numerous small branches and occasionally the death of a tree.

The scales do not eat the leaves so this eaten part sounds like a caterpillar type insect. Unless you can see one of these insects it will be difficult to ID which one. And if none are present now there is no need to treat since they have done their damage and moved on in the life cycle.

Since most of the scales are on the leaves and it is late in the year and the tree is large it is going to be difficult to spray the trees foliage with an insecticide. There is a soil applied insecticide that will be picked up by the roots and carried to the leaves and when the insect sucks the plant juices they are killed. Soon the tree will start to shut down and the movement of water up the tree will slow. If you want to you can try treating the soil around the tree with Bayer Advanced Tree and Shrub Insect Control. It will take a couple of weeks before the insecticide will reach the top of tall trees. Depending on your location and the time the hardwood leaves change you may not have the two weeks left in this year. IF not wait until next spring and treat the tree and the control will last all season for the scales and the caterpillars. Check with your local garden type store for this product. Here is a web link to the product.

http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect...