Answer from David Williams (Agriculture Victoria):
Granulosis virus is widely used by organic growers to control Codling Moth (CM) and increasingly orchardists are using it to reduce pesticide use.
It does work, however the problem is that you will still get some stings. Basically, the grub has to eat the virus, so the first bite it takes on the skin of the fruit is when it ingests the virus.
If you have high populations of CM the virus is not a cure-all solution, but it is useful if you can use it in combination with other things. At Agriculture Victoria, we have been looking at an ideal situation of Mastrus ridens controlling CM over winter to reduce overwintering population, hopefully achieving a population that is low enough for mating disruption to work. After mating disruption, if a few do lay eggs, there are some egg parasitoids around like Trichogramma or an oil spray could be used. After all this, whatever survives can be addressed by Granulosis virus. That gives a full suite of controls. For most conventional growers, if you have low populations then the virus can be the way to go.