Some years the native pollinators may be capable of providing adequate 
pollination (in a crop such as wild blueberries.)

In economics the term "Some" doesn't work out all that well.

Growers can import and flood an area with honey bees to make sure that 
good pollination happens.  Renting honey bees is a form of insurance.  
I've heard of (from a migratory beekeeper) of rates as high as seven 
colonies per acre placed on wild blueberries.

If you are buying insurance you may tend to care less fervently for the 
native pollinators in terms of ag chemical usage and 
developing/maintaining diverse year round forage.

I attended a wild blueberry growers' workshop this spring - I was the 
only beekeeper there.  The workshop was over seen by U Maine's Frank 
Drummond and I have a nice acrylic block on my desk somewhere (that we 
were given at the workshop) with native bees inside it. Dr. Drummond 
took us out in one of the blueberry fields and demonstrated how he 
monitors plant visits.  Based on what we saw, the arranged for honey 
bees not having arrived yet, native pollinators certainly contribute to 
achieving wild blueberry pollination.

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