I am in Sydney, Australia. This coming (arrived?) summer I have several fruit trees which will be bearing fruit for the first time. This includes a peach tree and nectarine (both of which already have masses of fruit about half the size of a golfball) and 5 different guava varieties, some of which are starting to flower at present.
In my particular area I don't know the extent of the fruit fly population, but it's a safe bet that they will be present to some extent. I have been keeping an eye on the peach and nectarine trees with no signs of infestation yet (as far as my untrained eye can tell).
Should I be taking a preventative measure right now, such as setting some baited traps? If an infestation takes hold, I'd like to use the most organicy remedy possible but I'm prepared to use pesticides to save the crop if there are no other options left. I'd much rather make a pre-emptive strike though, but I have no experience with growing fruit fly susceptible fruit trees. Any tips?