[David Bracey]

Alisdair at best its to measure the infestation todecide the optimum time to treat with something effective!  Not sure about Ammonium bicarbonate.

You could also use sticky traps to catch the adult moth. Where is strategically? In my experience most of the olives are produced on the South side of the tree which is the prevailing wind side.  Is this the location?

[David Bracey]

Am bicarbonate is USDA approved for use in a 3-way trap.  Am carb is an attractant because it gives of ammonia which attracts the adult olive fly, a male pheromone and a conventional insecticide such as delta methrin or similar which kills the moth by contact.

These are hung throughout the olive orchard.

[SandraC]

Thanks Alistair and David B for the various comments - 50g per litre would I suppose give me 20 trees-worth, so about 1.50€ per tree, which if it works would be ok (the best price for the green stickies is over 4€)...I think the loved-up male (according to Cheverel's article) is supposed to be attracted and then drown... Both methods of course are likely to attract other flies...tant pis...the only realistic organic alternative is spraying with a clay solution, which of course would have to be repeated every time there was a storm, and even so to get the right coverage seems like a very tiresome occupation...

I shall carry on regardless, and report what happens - i might try the yeast as well...thanks Marilyn in an earlier post..

Sandra