Question
I have several hibiscus that have done beautifully this year, but the last couple of weeks I have noticed some sort of disease on the top of the stems. It looks like a cross between fake snow and mold.  How do I treat this and what is it?  Thanks

Answer
The problem could be caused be two things.  One would be powdery mildew fungus.  This material can be wiped off with your fingers and will look normal for a few days until it grows back.  It will be fairly thin and not as cottony as the second possible cause, which is an insect called scale.  The scale cotton will be thicker and sort of gooey, where the mildew will be dry.  You will also find a small bug inside the scale cotton which will be squishy.  Each of these are treated differently.  The insect can be easiest treated with Bayer Advanced Tree and Shrub Insecticide.  This product is mixed with water and poured on the soil around the base of the plant.  It is taken up systemically and will kill the bugs within a week or so.  It also provides protection from reinfestation for up to a year. The mildew can be treated with a mixture of one tablespoon of baking soda and one tablespoon of light cooking oil mixed with a gallon of water.  Shake well to mix the oil and water.  Spray the plant to runoff and re-treat every 4-5 days for a total of 3 treatments.  Then sit back and see if you see any more mildew develop on the leaves.  If you do, treat again.  I hope these suggestions will help to fix the problem.  Good Luck.