White spots killing branches
hi, I had a dwarf nandina plant, very bushy, that had little white spots on the branches. It began killing the plant so much that I had to chop it down and remove it. I said, thank goodness the sky pencil holly is healthy, now guess what? I noticed some brown leaves and looked inside the plant (also very dense) and it has started there now as well. the white spots are less than a centimeter in diameter, slightly raised in the center. I don't know if it's mold, and what to do about it. I'd love to save this holly. Thanks for your help!
New Castle County Delaware
Both nandina and hollies are famous for harboring scale insects. The raised white spots you saw/are seeing are the waxy coverings of the eggs. If you watch carefully you may see the tiny hatchlings as they crawl around looking for food; this happens annually at about this time. Spraying the active crawlers is the best possible method of control. Nothing aggressive is needed; horticultural soap or oil will work well.
Unless the infestation is incredibly dense on an otherwise-weakened plant, scale will not kill your plants. Scale insects have numerous natural enemies.
See also https://www.extension.umd.edu/sites/default/.../Scales-UnivOfMD.pdf
Thank you. Looking at it today, I can see that the spots are actually kind of light brown. is it the same thing, scale insects?
Nandinas are hardy plants that have few insect or disease issues that are serious. Nandinas have suffered some from the cold winter we had this year.
Hollies are susceptible to a variety of different scale insects and these often have white to their coloration depending on the time of year. For proper identification of your problem, we need to see an example of the damage or suspected insect you are finding on your plant. Armored scale are quite capable of killing plants. Please bring a sample into the nearest cooperative extension office(461 Wyoming Road) for diagnosis. After we have the insect identified, we can provide you with options for managing the pest. Horticultural oil or insecticidal soap are possible solutions for scale management; however, it is critical to have the time of application correct. Thus, the need for accurate insect identification.