Experts and BHG readers answer.
White Spots/Sacs on Tree branches.
It sounds as though your tree has mealybugs. These soft-bodied insects are covered in white waxy material. As they feed on the plant, sucking the plant sap, they excrete honeydew, a sticky, sugary substance that would attract ants and possibly yellow jackets. The black coating that you see is sooty mold, a type of fungus which grows in the honeydew. If you can control the mealybugs, all the other problems should go away too. Because the mealybugs are wax-coated, it can be difficult to control them. Use an insecticide with a spreader-sticker, or use summer-weight horticultural oil to manage the mealybugs.