 stems or the chunks of them are getting a black, like a growth on them. That's correct. That's sooty mold. Sooty mold is the leftovers of the damage from lace bugs. Andromeda gets specific insects and it's called the Andromeda lace bug. And the treatment would have been, if you had caught earlier, a oil spray in March, a dormant spray, or now you have to hit them with a product called the systemic insecticide.