The following was received via email: I have a question about my neighbors Magnolia tree - something very bizarre is happening to it! I think it is a bush-type magnolia; in any case it's about 6 yrs. old and is about 6 ft. tall. A month ago yellow-jackets (bees) started swarming around it although there is no hive in the tree. We saw some very weird stuff on the branches (smaller, upper branches): brown, knobby things like popcorn kernals covering the branches, with black stuff, sort of like a thin black tar dripping down the leaves. It's even dripped down to some smaller bushes below it. What is this? Do you know? There are HUNDREDS of bees in this tree! Thank you for any information you can give me! Pamela, a.k.a. Loyalhedwig
Maybe scale insects emitting honeydew that is being covered by sooty mold fungus. Yellowjackets (bees are something else) are attracted to the honeydew, or are hunting for prey (they are predatory) on the shrub anyway.
I agree with the prior assessment. A Volk oil or oil/detergent spray should eliminate the scale/aphid/mealy bug (whatever) infestation and the rain or watering will slowly eliminate the sooty mold. Since the honeydew is the sustaining nutrient for the sooty mold, removing the critters removes the rest in succession. Voila! No hornets!
