Lecanium Scale is a very serious problem with our oaks in Charlotte. It has been around for many years, but I am seeing a major increase on residential trees and street trees. Several years ago I photographed some Lecanium Scale that came from the top of one of the willow oaks in my yard. I happened to capture some good photos of both the scale and the crawler stage which how it spreads.
Over the years we have removed 6 or 7 large willow oaks from the yard and are down to just one reasonably large, very healthy willow oak in the back yard. When these trees were removed, we removed the stumps and planted new trees in some of the voids. One small tree was under the willow oak where I got the sample of Lecanium Scale and I was not surprised to find Lecanium scale starting to take hold of the smaller tree this season in 2015, All the above happened in 2013,
This year 2015 two years later, there were crawlers on the small willow oak that we moved from the front yard to the back yard. I found that spraying the small tree in the crawler stage did a good job of controlling the insects on the smaller tree, but I can only spray about 7 feet from the ground. There are systemic insecticides that will work by absorbing the material through the roots or foliage..
I had a similar problem when I had lots of Fall Cankerworms on this same tree and I sprayed them effectively, but could not reach all the way to the top of the tree. The upper portion of the tree was stripped of small leaves and buds by the fall cankerworm. New leaves are starting out.
In photo below I turned to get the top of the tree in the light background of the sky. You can see that there is no foliage in the top but the lower foliage looks good. Recently I hand picked off several Lecanium Scales adults.
The tree above has had several problems. It was planted with a tree spade and moved from the front yard to the back yard. The tree was planted a little too deep and there were some air gaps around the root ball after planting. I got out the air gaps and “mudded” it in. I believe the top of the tree will leaf out as the season is still quite young. I will keep and eye the tree.