Wilding pine costs could soar past $4b

Better to bring in an insect that eats pine trees. (but only the wild ones)

that would be the Wilding Pine Eating Insect...

Well, I would argue introducing non-native insect is far riskier to the NZ ecosystem than introducing a sterile strain of a commercial tree that is already here. Still it is a viable option with the right risk assessment. I see the EPA has approved a number of biological control agents in recent years - more than I expected actually. https://www.epa.govt.nz/industry-areas/new-organisms/biological-control-agents/

Reality is all wilding pines have commercially planted siblings. No biological weapon will kill one without killing the other. I think wandering the hills with a grubber and chainsaw are going to be the main method of attack for a while yet