I have several old roses in planters. The bark on one of them has been peeling off for several years. You can touch it, and the bark drops off. Another rose bush near it looks as though it has the same problem. Can this problem be contagious? I can't find any references to this in my gardening books.
This may or may not be a problem at all. The bark on older roses will easily peel off, especially below the bud union. The bud union is where a rose is grafted onto a rootstock.
I wouldn't be overly concerned if the tissue in this area shows no noticeable discoloration other than a dark brown. It would help if you closely inspected the canes above the graft for any damage from sunburn on the side that receives the heat of the day sun or from a physical injury. Damage from sunburn causes the tissue to turn black.
The current year's growth is usually green compared to the brown or tan of the older canes. The canopy of the rose itself typically protects the canes. The leaves or foliage acts as a natural sunblock.
Sunburn and peeling bark are a bigger issue with tree roses because of the exposed trunk. Again, the damaged areas will turn black and can be an entry point for Flathead Borers.
Borers will not attack any healthy tissue. You can locate them by scraping the bark with a knife as they are right under the surface. Borers are white or amber-colored, usually linear in shape, and are easily seen with the naked eye.
There isn't a simple answer to protecting the trunk(s) other than the natural shading from a full canopy. You could paint the trunk(s) with white latex paint or wrap them with shade cloth when the afternoon temperatures are above eighty-five degrees.
I have been unsuccessful in controlling Mealybugs on my houseplants. I have used sprays, dust, and alcohol to remove them. What would you suggest?
Mealybug is a common problem with indoor plants. You can also find it on woody ornamental like pyracantha and cotoneaster,
They're easily recognized by the copious amount of cottony wax material they produce An adult female deposits eggs in the cottony mass surrounding her body.
The eggs hatch within a week or so, and the nymphs migrate over the plant until they find a suitable resting place and start feeding on it. Several generations per year are typical.
The Mealybug population thrives on plants with succulent growth, sometimes created from over-fermentation but more likely from warmth and humidity relative to the amount of light.
I suggest you control them with a systemic granular insecticide applied to the soil and absorbed into the plant. These granules are reapplied every six weeks. This allows you to manage the problem effectively instead of having it be a headache.