What is this strange bug?
It swarms only on one certain plant with trumpet-shaped red flowers (in the picture the flowers are all shriveled and the leaves are in the foreground) and totally coats it until the bush dries up. It spreads very rapidly but only to this particular plant - will not touch any other. The bugs don't noticeably move, giving the impression that the whole bush has developed white fur.
And it seems the plant is a hibiscus: http://homeguides.sfgate.com/hibiscus-leaf-87355.html