Wednesday, July 29, 2009
Stem Dieback on 'Sky Pencil' Holly
When a plant in the garden starts to lose leaves and look bad, the first instinct is to water it more or fertilize it- and that may be all it needs to thrive.
But before you make a change, get closer and check out your plant for insects, disease or other problems.
When I first saw this plant, I thought that it probably was not getting enough water. It's the middle of summer, and there is not a lot of room for the roots to find water between the bricks and the wall.
But when I looked at the dead stems, I saw that they were bumpy instead of smooth like they should have been. The holly was infested with a type of scale insect. I call them "false bark scales" because they are the same color as the bark and blend in very well.
If you scrape your nail over the bark, these immobile insects will come off.
Insecticides are not useful for treating bark scales- they just won't work. The best thing to do is prune off all of dead and dying stems (removing the insects). If there are a few more on the healthy parts of the plant, just scrape them off. When the weather is cool, coat the leaves with a horticultural-grade oil to smother any that you missed.