Foiling The Fruit Fly

Fruit flies are on the move, spreading into new areas and destroying backyard fruit crops. The damage these little flies cause has to be seen to be believed. Anyone with fruit trees in their garden needs to give some thought now to how they intend to control this devastating pest.

If you or your neighbours had this problem last year, be prepared for a repeat of the same, unless you take measures to prevent it.

I’ll give you a choice of several strategies you can use to prevent infestation this year. There a number of baits and traps commercially available. Last year, after having to sacrifice almost the whole fruit crop after fruit flies infested my peaches and plums, I bought a trap called Cera Trap. This consists of jars containing a liquid that attracts and kills both Queensland and Mediterranean fruit flies. With several of these hung around the garden, there was very little infestation in the summer tomato crop. Those tomatoes in which there were larvae developing were solarised, as above.

This year, I have the traps ready to hang as soon as new fruit begins to form, which will be very soon as I have peach and nectarine trees in blossom right now. With luck, and cooperative neighbours, I’ll prevent a recurrence of last year’s disaster. I bought these traps through an organic gardening mail order company called Green Harvest. They also sell exclusion bags to cover the fruit and another bait product, which works similarly to the Yates product described below (www.greenharvest.com.au or ph: 1800-681-014). I know there are people who are happy to use the exclusion bags, and covering the fruit this way would probably keep the pests off (you have to be careful not to leave any gap for the flies to enter). However, to me they seem like a lot of fiddle, and what happens with the fruit you can’t reach to put the covers on?

Yates Nature’s Way Fruit Fly Control has the advantage of being readily available. You can probably get it at most garden supply shops. It is made from spinosad and a protein and sugar-based bait. Spinosad is an insecticide made from naturally occurring beneficial soil bacteria; this kills the fruit flies after they have been attracted by the bait, which the flies can detect from several metres away. This product is applied to the trunk and lower foliage of the trees.

When using a product such as that described above, you need to put out several traps around the fruit trees NOW, to monitor for the presence of the flies and know when to apply the bait/insecticide. There are numerous homemade traps and baits, I’ll only give the bait recipe suggested on the Yates website: 1 litre water, 1 cup brown sugar, 1 tablespoon yeast, 1 tablespoon Vegemite, ½ cup cloudy ammonia. Combine well and put a small amount into a several plastic bottles hung from the fruit trees. The bottles need to have small holes or a flap to allow the flies to enter.

Both methods described are suitable for use in organic gardens.

Garden hygiene is paramount throughout the spring and summer. During and at the end of the fruit harvest each year remove all fallen and mummified fruit and solarise it or dispose of it in the rubbish bin, not the compost. To solarise infected fruits, or weeds for that matter, place them in a sturdy black plastic bag and leave it in the sun for up to six weeks (during the summer). By this time any pests will be cooked and the rotten fruit can safely be added to the compost. Do not use the biodegradable bags as these will break down when exposed to sunshine for lengthy periods and you will end up with a mess of small bits of plastic and rotten fruit.  

Alternatively, if you have poultry, feed them the infected fruit, just make sure it is all eaten.

As a general aid to control of fruit flies and numerous other pests, plant trees and shrubs to attract insect-eating birds, keep soil and plants healthy by using organic fertilisers and always remove fallen fruit as soon as possible. 

Fruit fly control products do cost money, but if you don’t use them you will lose the fruit and be responsible for the spread of these pests into nearby gardens. Having seen the destruction first-hand, I am now hesitant to recommend that anyone rely on homemade traps/baits to control them, except for monitoring. If you are not willing or able to take appropriate care of your backyard fruit trees to prevent the spread of fruit flies, for goodness sake get rid of them altogether and replace them with non-fruiting trees or shrubs. Do it now.