Hi, , sounds like
Bay Suckers
For reference check

http://www.rhs.org.uk/advice/profiles0500/sucker.asp
and
http://www.gardenersworld.com/how-to/problem-solving/garden-pests-bay-leaf-suckers/

Depends how large your tree is you can either pick the affected leaves one by one or spray with Provado Ultimate Bug Killer Ready To Use ( you can use the concentrate if it is for a big plant ).

If you are to spray, don't forget to pick as many leaves as you might need to use up for 2-3 weeks and either freeze them or dry them.
hope this helps...

"White stuff" could mean a lot of things, including bay sucker, but also scale insect infestation or mildew