Blossom abounds . . but no bees . .

Lots of blossom this year - 2013 - but no bees

Bees nesting in birdbox last year -2012

Am surrounded by blossom in the garden - but not a bee in sight, whereas last year they settled in one of the bird boxes. Very worrying.
Does this mean I have to go round dusting the blossom with a soft paintbrush to ensure an apple crop?