Posted: 03/10/2013 at 14:21
Sounds like scale insects - remove them with your thumb nail or dab them thoroughly with a cotton bud soaked in meths.
The bay tree has probably had some aphids on it - they excrete honeydew which is what the insects (possbly hoverfles, possibly wasps) have been after. The honeydew gets mildewed and turns black. It should be easy enough to remove from the patio with soap and water and elbow grease, or a proprietory patio cleaner.
As for the bay, I would remove the scale insects give the tree a good hosing (not a jet wash but a good strength squirting) to help wash off what remains of the aphids and honeydew - the winter rains will do the rest.
In the spring repot your bay into some good quality compost and feed it regularly - it's weak plants that get damaged by insect pests.