Good idea in theory, Nobby, but... as you say Ma Nature will have her 2c

“Amongst other things, the trials imply risks for the olive farmers. If the genetically engineered flies escape, the harvest in the regions concerned would become nonmarketable. Genetically engineered larvae living inside the olives are not allowed for food consumption in the EU”, says Christoph Then for Testbiotech. “While the female descendants are supposed to die as larvae, the male individuals can survive for several months, mate and propagate further. If they escape, which according to the application of Oxitec, can not be excluded, they can move into the the environment and spread without control. Olive flies are able to fly over distances of several kilometers.”