Black sooty deposit on trees and bamboo

We have a few trees (orange, yuka and bottle brush) and a lot of cane (like bamboo) in our yard and all have varying degrees of the same issue.  There is a layer of black funkiness that is on many of the leaves.  It is kind like dirt but usually in small dots, and often only on the underside of the leaves.  We think it is some kind of pest poop.  The trees seems mostly healthy aside from that, although they could probably use some extra love too.  

Looking for recommendations for someone to help address this issue. Ideally someone who can teach us what needs to be done, if it needs repeat treatments.  Would consider hiring someone to do repeat treatments (as we assume this will be an ongoing issue) only if very affordable.  Really wanting to just pay for the expertise of what needs to be done. 

Thank you!

Parent Replies

New responses are no longer being accepted.

It sounds like you have an infestation of soft-bodied insects (probably aphids) on your bamboo, which is very common. The insects' waste (honeydew) creates the environment for sooty mold. I hear it's treatable, but we ended up removing our bamboo instead. It kept falling on everything and our bamboo was very tall, so the common solution (wiping off the sooty mold and eliminating the insect problem) wasn't feasible. We did get a bit of an improvement one year by releasing 5,000 ladybugs. They feed on aphids and they helped reduce their the end, there was no non-toxic approach that worked, but again, if your bamboo is not extremely tall, you probably have a better shot. Good luck!