There's one thing getting in the way of Australia's great tomato-growing climate and us enjoying bumper crops of tomatoes – and that's the fruit fly. This tiny insect likes to lay its eggs in all sorts of fruits, including tomatoes. When the eggs hatch into grubs inside the fruit, it is quickly ruined. It's so disappointing to cut open a tomato and find someone else, a lousy little larva, already enjoying it. Fink.
The closer you get to the tropics the worse the problems with this pest become, but temperate Sydney is plenty warm enough for this insect to be a serious pest here too. As most of us backyard food gardeners are doing everything organically, the big problem is controlling insect pests organically. It's not easy.
It certainly can be done, but it needs persistence to succeed. Fortunately I am just the sort of persistent nutter that organic gardening needs as a recruit, and so I thought I'd do a blog about the two different organic pest control methods I am using this summer to control fruit fly. One is hi-tech and uses modern, organic, low-toxic products which are the results of excellent science. The other is low-tech and comes from my kitchen cupboard. Both work.
First, the hi-tech gear. Both Nature's Way Fruit Fly Control and Eco-Naturalure are based on Spinosad, which is derived from naturally occurring soil bacteria. This ingredient is now widely used to control various insect pests in gardening and commercial agriculture. When you open the bottles, both products are a thick black gloop which you mix up in a small spray bottle with water, and spray near (but not on) the crops you want to protect.
You should not spray the product on the fruit itself, as it is designed to attract the insects. Once they ingest the liquid, it then kills them. Pictured here, it's sprayed on an outlying tomato plant leaf (I spray it in several spots each time, and not in the same spot repeatedly, as doing that can lead to other problems such as sooty mildew).Each product sounds great in theory and works OK in practice, but they do wash off in rain, so you need to re-apply them after rain. And you need to reapply them after several days anyway. You absolutely need to fully read the label before using either product. They are safe to use and won't harm you or your plants, so that isn't why you need to read the label. You just need to mix it up correctly, then re-apply it fairly often in the right places and at the right time. Use it incorrectly and it might not work, and as they aren't cheap that's just a major waste of money.
However, as a back-up system to the fancy products I have also set up a Vegemite trap for fruit flies. This worked well last year, but be warned, it catches lots of ordinary flies, not just fruit flies. It's gruesomely effective! So here we go...
If you don't know what Vegemite is you obviously aren't Australian. Ask an Aussie about it the next time you meet one. It's a breakfast spread for toast or bread. However, it is an 'acquired taste' that should be spread very thinly, especially if you're a Vegemite newbie. I love it, as many Aussies do. For a fruit fly trap you need 1 heaped teaspoon Vegemite, dissolved in 500ml warm water.
The warm water just makes it easier to dissolve the Vegemite. Give it several good stirs, as it does take a while for all of it to dissolve. 
Next, pour the liquid into your trap. To make your trap you'll need a couple of clear plastic soft drink bottles and a bit of wire to hang it up somewhere.
This is a fairly deluxe Vegemite fruit fly trap, actually. We cut the top few inches off one plastic drink bottle to make our 'entrance' funnel, then cut a hole in side of another bottle and stuffed the funnel in. A simpler design is to just make several holes around the middle of the bottle to allow the flies to enter the bottle and find out what is that alluring smell in there!
As you can see, this large entrance funnel just makes it a little easier for the flies to land and wander in. Or at least that's the theory.
In the top of the bottle, just under the screw cap, we punched a hole in either side and threaded some wire through to make a handle to hang the trap somewhere. Last year we hung it near some tall staking tomatoes, and God it looked ugly!
So this year I have discreetly placed the aesthetically-challenged killing machine very close to my Alaska tomato plants and hopefully it will prove as deadly and attractive as it was last year. I've watched these fruit flies in action, and they are great wanderers and seekers. I am sure they will find my trap, check in but never check out.
Finally, the reason for all this dastardly insect warfare – my babies. The Alaskas ripen daily, so too the Beaver Lodge Slicers across the way. The taste test is only days away, and I don't want to cut open my first tomatoes and find grubs inside. Now that would be a horror movie!
