Mildew growth on Hibiscus Leaves

Hi,

I noticed a couple of my Hibiscus plants' leaves turning yellow. I realized they were stressed so I looked carefully at the plants and found that the yellowing leaves had some kind of black mildew/fungus growing on the bottom surface of these leaves. Does anyone have any suggestion(s) on how to get rid of this nuisance?

Thank you for your time and help.

It could be honey dew from aphids. Spray the plants with insecticidal soap. That should get rid of the aphids.
Barb

Pictures would help, but I think Barb is right. There's black stuff called sooty mold that grows on the honeydew secreted by aphids, mealybugs, scale, etc. The mold itself doesn't hurt the plant (unless it completely covers too many of the leaves) but the insects that are making the honeydew can definitely cause problems.

Thank you for the replies. I have tries spraying with oil/soap solution, soap/alcohol solution and a couple other organic remedies but the yellowing and the mold/mildew did not go away. I do not see any aphids, but there are insects in the garden, so the other suspects are to blame. I have decided to bite the bullet and get a package a Safari to treat my hibs. Seeing them stressed makes me feel bad and I want to make it better for them!!!

If it is sooty mold on top of honeydew, it's pretty hard to get that off the leaves since the honeydew is very sticky. And yellow leaves generally won't go back to being green, so I'm not necessarily surprised you didn't notice any difference after spraying (but if there were aphids there, you probably killed them with all the sprays which might be why you don't see any now).

Can you post some pics of the mold & the yellowing? That might give people some other ideas of what's going on.

Thank you for your concern.

Here is a sample of the yellowing leaves.

If you look closely, you can see the black mildew growing on the back of the leaf.

Hope this helps to identify the problem.

Thank you for your time.