Olive fly

What you see

A small tan fly with a dark spot at each wing tip, about 5 mm, that hovers around the fruit in late summer. The giveaway is on the olive itself: a tiny brown sting mark, later a small exit hole.

Damage

Pin-prick brown punctures on green olives from July. Later, a soft brown tunnel inside the flesh and a 1-2 mm exit hole. Fruit drops early; oil from stung olives has high acidity and poor flavour.

Lifecycle on this coast

Two to four generations a year here. The female lays a single egg under the skin of each olive; the maggot eats the flesh around the stone and pupates inside the fruit or in the soil beneath the tree.

When to act

This one has essentially no tolerance if you want table olives or good oil - a 10 percent sting rate already spoils an oil batch. Trap from June to know when they arrive, and protect before the first sting rather than after.

Months: June, July, August, September, October, November

Plants it bothers

Olive

Natural enemies

Parasitic wasp (Psyttalia), Ground beetle, Bat

Remedies

Kaolin clay film, Pheromone traps, Bordeaux mixture (copper)

The thing people get wrong

Kaolin is your real defence and it is a calendar job, not a reaction. Get the trees visibly white from the time olives reach a centimetre, keep them white through September, and collect every fallen olive off the ground - each dropped fruit is a nursery for the next generation.