Question
A week ago I noticed my 3 hibiscus with a white cotton like strands hanging off the underside of the leaves. On closer inspection there seem to be small bugs living and making these strands.  I'd appreciate any clue as to what they are, and advice on what to do.

Answer
They are most likely scale insects and they need to be controlled.  The best way is with a systemic insecticide.  I would treat the plant 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.  You can find this product at Lowes or home Depot.  Works Good.  Good Luck.