Forbidden Fly: Bio-securing a Suburb

“Have any more Queensland fruit flies been found in Avondale since the one a few weeks ago?”, asked a Canadian friend. Lindy is a great gardener and gatherer of things that grow on trees. She’s stayed at my home in that suburb so she was interested to learn that scientists had trapped one of these pest insects nearby.

We don’t usually have Bactrocera tryoni in New Zealand. Females of this species are notorious for injecting their eggs into fruit when it approaches what growers consider to be perfection. On the other hand our tiny, ubiquitous Drosophila fruit fly, from a different family altogether, arrives on a whiff of ferment: its females prefer a slightly past-it squishiness for their nurseries, rendering a less common name — vinegar fly — more appropriate.

Produce that’s infested with Queensland fruit fly larvae can’t be sold and will quickly rot. As Bactrocera tryoni likes more than 100 different kinds of fruit, the visiting Australian (a single male) caused quite a flap. 

Banana skin. Dropped outside
our place during the controls.

Our big new Ministry for Primary Industries responded to the discovery by setting up a “controlled area” of about 1.5km, from which whole fruit or vegetables were not to be moved. When I took a small bag of homegrown feijoas to my parents, who live several suburbs away, Dad asked quizzically if my address was in “the zone”. Luckily not: the boundary was a few houses away.

People within the zone were asked not to compost their fruit and vegetables. Signs went up on the borders, a lot more traps were installed, and Avondale’s Sunday market was abuzz with officials checking that buyers and sellers knew the rules. Yellow lidded bins were stationed at intervals along local roads for the disposal of produce from the controlled area.

It felt a bit like one of those patriotic wartime campaigns for the home front, and initially it was easy to get excited. But our primary industries people seemed to discourage digging for victory — within the zone, you weren’t supposed to move soil from under fruit trees. (Queensland fruit fly larvae pupate in soil.)

Amelia (New Hampshire Red),
very interested in some guavas.

Just outside the zone, a few more end-of-season feijoas plopped to the ground from our tree, my crabapple crop was ripening, and the chooks were enjoying the odd piece of fresh produce that went their way. I continued my small-scale composting operation.

In case that made me a bad person, I also topped the indoor compost bucket with shrink wrap, and entirely covered any fresh additions to the lidded outdoor bins with stinky chicken manure to repel boarders. I’d already been taking care to collect any fallen feijoas: rats had moved in a while before, and I didn’t want to offer them breakfast as well as bed.

We watched out for invaders in the form of flying machines — colourful ones, 7mm long. Within hours of the announcement about possible fugitive fruit flies, Carol caught one (she was pretty sure) when she was doing the dishes. The half-drowned creature went into secure confinement and my partner rang the hotline, whose responder said someone would come to collect it. They never showed. 

Unwanted: Queensland fruit fly
(Ministry for Primary Industries).

It’s hardly surprising: most of us humans are not even on nodding terms with the many insects in our environs, so our chances of correctly identifying a newcomer are slim. Most insects that are permanent residents don’t do major damage, though Carol’s brother-in-law regards mozzies* as his mortal enemy (the whine of their wingbeats as they approach means “I smell the blood of an English-man”). Perhaps our prisoner was one of those drab little miseries, though Carol has her doubts.

A lone male fruit fly is a bit like the proverbial single swallow, only instead of not making summer, it doesn’t a) make whoopie,
b) sow its wild oats, or
c) start a dynasty. 
So a fortnight after the fruit fly flurry began, and with no further sign of B. tryoni migrating across the ditch,** the restrictions on Avondale fruit and vege were quietly lifted. 

Two minutes’ walk from home.

Presumably our government and trading partners were satisfied that no new population of pests was being established, or perhaps the whole thing had been a dummy run. (Army officers hold exercises: why shouldn’t the officers of Ag and Fish?)

It’s a relief. Only a few years ago, some of Auckland was subjected to mass aerial spraying of a product to rid us of another unwanted Aussie, the painted apple moth. And though mass aerial bombardment would not have been undertaken for fruit flies, there would have been changes. 

We would have had to be diligent about collecting fruit from our trees, preferably before it fell. Composting would have been curtailed. A series of chemotherapy treatments may have been the lot of my largely organic garden plot. Distribution of home-grown fruit and vege to folks beyond the Avondale border would probably have come to an abrupt halt. The silvereyes would have found fewer crabapples to eat, and The Good Life would have been a little less so.

Home-grown feijoas, from the last of the
season’s harvest. (Bowl courtesy of Jocelyn;
food styling by Claire.)

*An abbreviation of mosquitoes, used frequently in New Zealand but originally from Australia, even if the insects themselves are our own.
** The ditch is the Tasman Sea between NZ and Oz. It’s pronounced dutch, if you’re a Kiwi; deech, if you’re an Aussie.

Sources and Interesting Reading
www.fightthefruitfly.org/information.html
www.daff.qld.gov.au/26_17828.htm
Which New Zealand Insect? Andrew Crowe;
New Encyclopedia of Insects and their Allies,
ed Christopher O’Toole (accessed through Oxford Reference Online)