Mediterranean fruit fly

What you are looking at

A small, dark pinprick mark on the skin of ripening fruit, where a female has punctured the surface to lay eggs beneath. Over the following days a soft, discoloured, sunken patch develops around the sting as the fruit begins to rot from the inside, and cutting an affected fruit open usually turns up small white to cream maggots tunnelling through the flesh. Sometimes the first sign noticed is fruit falling before it would otherwise be ready, already carrying damage that is not obvious from outside.

The adult responsible is a small, striking fly, only 4 to 5 mm long but boldly patterned in mottled yellow, brown and black, with clear wings marked in distinctive dark and yellow bands, quite unlike the plainer reddish-brown appearance of many other fruit flies.

One of the world’s most damaging and adaptable fruit pests

Native to sub-Saharan Africa, this fly has become one of the most widely distributed fruit pests on earth, attacking more than 300 different kinds of fruit and vegetable and established across the Mediterranean basin, the Middle East, much of Central and South America, Hawaii and the south-west corner of Western Australia. In Australia it once occupied the eastern mainland too, before Queensland fruit fly, a more mobile and prolific competitor, displaced it there over the twentieth century, leaving Western Australia as its last Australian foothold.

It has repeatedly turned up in California, Florida and Texas, arriving in infested fruit carried by travellers or through the post, and every one of those incursions has triggered an eradication campaign, including large- scale sterile male releases, rather than being accepted as a permanent establishment. That pattern, an adaptable pest capable of breeding in a huge range of hosts, arriving repeatedly and being fought back each time, is likely to continue wherever fruit moves between regions faster than quarantine can screen it. New Zealand has never had it and treats a sighting as an immediate biosecurity matter.

What to do about it

Never move homegrown or backyard fruit out of a quarantine area, since this is one of the main ways the pest has spread and re-established after eradication campaigns.

Pick up and destroy fallen and infested fruit promptly, before larvae inside can complete their development in the soil beneath the tree.

Bag individual fruit or net a whole tree as it ripens where the pest is established locally, and use protein bait or pheromone traps to monitor for a rising population.

Support any area-wide sterile insect release programme running locally as the primary defence. Reserve a registered protein bait spray applied to foliage rather than fruit for a genuine outbreak that bagging, sanitation and trapping have not brought under control on their own.

Report a suspected sighting or damaged fruit outside the pest’s confirmed range, including mainland North America and New Zealand, to the national plant health or biosecurity authority immediately.

What it gets mistaken for

Queensland fruit fly has a plainer reddish-brown body and clear, unbanded wings, quite different from this species’ bold mottled pattern. The two occupy largely separate ground in Australia, Queensland fruit fly across the east and this species confined to the south-west of Western Australia, so a sighting in the wrong region for either is worth reporting on that basis alone.