Marshmallow Bush Is Leaking Black Oil Like Substance On Trunk And Branches

Question From: R. Foster - Salinas, California, United States
Q: I have a tall marshmallow single purple flower bush (althaea offinalis) that is leaking black oil all over the trunk and long branches. I scratched and a larva or worm wiggle out. I since cut the tree down but left about 8" growning on the bottom which didn't seem infected. What could this stain be and how should I treat the remaining trunk??

A: Rosie, I can't help you on this one. I live in Michigan and am not familiar with the bugs that live in California. Chances are the "black oil" is sooty mold which grows on the honey dew produced from aphids. Have no ideas what the larva was. Best bet is to keep an eye on the regrowth of the plant and if you see any signs of problems take a sample into your local independent garden center for an ID. Best And Happy Yardening, Nancy