Celebrate fruit fly detections in New Zealand

Posted by Prof Jacqueline Beggs @JacquelineBeggs

About to bite into that luscious, juicy taste of summer, a tree-ripened nectarine? Be thankful you do not live anywhere with fruit fly.  This group of insects are infamous for the damage they do to a wide range of fruit and vegetables.

Apricot (left) and pear (right) are two of the many fruits affected by fruit fly. Images used by permission Plant Health Australia

As well as summerfruit, they attack citrus, apples, pears, berries, grapes, olives, persimmons, tomatoes, capsicum, eggplant, and avocado. We are not talking a bit of cosmetic damage to the skin – fruit can end up as a soft, mushy, inedible mess. Fruit fly females lay eggs into fruit and the developing maggots munch away, causing the fruit to rot and drop to the ground.

The extent of damage can be devastating. The island of Nauru ended up home to four species of pest fruit fly.  By 1998, about 95% of mango were infested and island-grown fresh fruit and vegetables were so scarce locals had to rely on more expensive imported produce. Fortunately, an intensive lure and poison programme eradicated three of the four species and mango and breadfruit were back on the menu.

Australia is not so lucky. They have two highly damaging fruit fly species, the Queensland fruit fly and Mediterranean fruit fly. Commercial growers spend hundreds of millions of dollars on various control measures and quarantine measures are in place to try to stop the spread into uninfested areas. With varying degrees of success.

A single Queensland fruit fly (Bactrocera tryoni) was recently detected in Devonport, New Zealand. A full scale response has been triggered as it is regarded as a serious pest [Image: James Niland, Wikimedia commons ].

It is no surprise then that detection of two different species of fruit fly in New Zealand in a week makes headline news and our dollar falls. Finding a second Queensland fruit fly near to the first is concerning. We certainly do not want them to establish. However, I think we should also celebrate. The detections are really New Zealand’s biosecurity system operating at its best. We have in place a world class fruit fly detection system; a nationwide surveillance network of 7737 traps baited with fruit fly specific lures that are checked seasonally.

Including the three latest finds, this network has detected 13 incursions of economically important fruit flies since 1989.  More importantly, early detection and effective control means fruit flies have not established in New Zealand. With such high stakes, it is critical that we keep going with research to improve surveillance, eradication and control tools. Recent PhD work at University of Auckland by Dr Lloyd Stringer is a good example; he developed a population model that helps to identify the most successful management and eradication options for Queensland fruit fly.

We cannot afford to take our foot off the pedal. Fruit fly will keep pushing at our border since there are around 80 pest species found in many countries we trade with and travel to. Furthermore, some regions have given up trying to achieve area wide fruit fly control, leading to higher density of these pests. That makes it easier for an individual fly to slip past all the measures we have in place to keep them out. So hats off to all the folk involved in keeping fruit fly at bay. That includes you – letting biosecurity officers onto your property to check for infestation, making sure you do not move fruit or veges from “controlled areas”, and encouraging everyone to never bring undeclared produce into New Zealand.

Prof Jacqueline Beggs is Director of the Centre for Biodiversity and Biosecurity, a member of the Biosecurity Ministerial Advisory Committee and co-supervised Dr Lloyd Stringer for his PhD research. And nectarines are probably her favourite fruit!

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