Fungus on Otto Luyken
I seem to have a fungus on my Otto Luyken plant. It killed an entire branch, which I cut off last week. The branches are covered with a white fungus. It looks like powdery mildew to me. I sprayed it with a mild solution that seems to have helped, but not completely. The plant has good circulation and it is cold outside. I thought those things discouraged powdery mildew. Is the problem something else? I am grateful for your help. I have attached photos. The fungus seems to be mostly underneath the banches on the ground side. That may be because I didn't spray the underside well with the milk solution. Thanks!
Montgomery County Maryland
What you are seeing is not a fungus or powdery mildew.
It is actually an infestation of a type of sucking insect called scale, perhaps 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.
You are on the right track with the removal of the dying limb.
You can also gently scrape off as much of the scale as you can.
Horticultural oil sprays can be helpful for control.
Here is our page on scale insects: http://www.extension.umd.edu/hgic/plants/armored-hard-scale-trees-and-shrubs
Incidentally, we don't recommend spraying a milk solution for powdery mildew. More about that problem here: http://www.extension.umd.edu/hgic/powdery-mildew-trees-and-shrubs