Diseased limbs on Sckip Laurels
Hello, just noticed that our Laurels on the sunny side of the house have a lot of dead leaves (brown). On further checking the limbs are all covered in something white. Can this be powdery mildew or something else and is it treatable? Thank you.
Howard County Maryland
What you are seeing is not powdery mildew.
It is actually an infestation of a type of sucking insect called scale, white prunicola scale. They don't look at all like what we traditionally think insects look like, and they are in fact the bumps on the wood, which you should be able to pop off or dislodge with your fingernail. They are stationary under those covers for most of their life cycle. They suck plant juices.
Scale insects are difficult to control.
You can gently scrape off as much of the scale as you can, then spray with a dormant rate of horticultural oil to smother overwintering scale. Once the plant leafs out, remove any dead wood and prune out branches with severe symptoms. In June, keep watch for salmon-colored tiny crawlers and spray again if you see them. Natural parasites generally provide control of many scale infestations. To protect parasites, avoid spraying with insecticides during the summer.
Also keep trees and shrubs watered during droughty periods and do not overfertilize.
Here is our page on scale.White prunicola scale is an armored scale: http://www.extension.umd.edu/hgic/plants/armored-hard-scale-trees-and-shrubs
Thank so much. They are just covered so impossible to scrape everywhere so will have to reset to spraying. Thank you again for your reply.