We scored a whole bag of mandarins from some friends last weekend, only to find that they were riddled with fruit flies – well, baby maggots to be precise. My daughter had picked them directly from the tree and there was not even a hint of disturbance to these gorgeous citrus. To the untrained eye, they even looked better than the shop-bought varieties.

Fruit flies will damage your fruiting harvest

Peel away the skin and the flesh began moving more than the ceiling after a hard night. Fly larvae – maggots – were wriggling through the fruit intent on devouring as much as they could. Instantly the adage “Don’t judge a book by it’s cover” flooded my memory as I disappointedly began checking the rest.

One or two were free of the infestation but the majority were write-offs. Given another week or two these fruit would begin rotting on the tree providing a glorious dwelling and upbringing for the next generation of these pests.

I should have taken the cue “We didn’t get the tree sprayed this year!” as a major hint that fruit flies may have been a problem in the area. Instead I thought, “Great, these people grow their fruit organically”. Doh, Doh!

How can you stop fruit flies from infesting your fruit?

Prevention is obviously the first place to start. Traditionally most people have used chemical sprays once the fruit has set and before it begins to mature. Fruit bought from retail outlets usually undergoes two sprays – pre-harvest and post-harvest. The post-harvest pesticide is to combat infestations that may occur while in transit and before the consumer eventually eats it.

While most pesticides used to treat fruit flies are fairly sedate they work by inhibiting cholinesterase – an enzyme required by the animal kingdom for proper nerve functioning. While these inhibitors work wonders on fruit fly in minute amounts if the dosage were increased it could cause nausea, stomach cramps, blurred vision and even an increase in your heart rate. Hardly something you might consider as you begin munching into your mandarin.

While spraying may be the easiest method of fly control the side effects and health concerns for parents are obvious. Therefore, organic eradication is slightly more attractive.

The best way to start is with a trap of some description. Some use jars suspended from the fruit tree while others have more elaborate traps (aff.) set to catch thousands of unwanted flies.

The trick with making these work is as follows;

  1. Offer an attractant

    Fruit flies are drawn by the scent of the maturing fruit. Therefore, offer them a counterpart aroma that seems equally, if not more, desirable. Honey, vinegar, sugared water are all good baits.

  2. Create an entrance

    The welcome mat for your fly trap needs to be large enough to allow them in without persuading birds to think they have a chance as well.

  3. Remove any exits

    While the entrance should be clearly marked and freely admissible, any exits should be cut off. The use of funnels is a great way to produce this result.

These are the basics of any organic fruit fly control. It’s quite simple in its manufacture and easy to maintain though you can see why some people prefer pesticides as the set-and-forget method.

What to do with fly-ridden fruit?

Definitely don’t throw it in the garbage or on the compost heap. These are both perfect breeding conditions for fruit flies and instead they should be destroyed.

One method offered by various government websites is to soak them in kerosene. The problem with that is kerosene is hardly an organic resource. So I tried two different methods with our spoilt fruit. The first was in a bucket of water and while the fruit had to be kept from floating it did eventually do the job – it took two days though.

The second method was using oil – the plain old cooking variety. The maggots were dead within 12 hours (it may have been sooner but I didn’t check them for half a day). The obvious problem with this method was what to do with the fruit once the maggots had been killed. The only option was to put them in the garbage while the fruit covered with water could then either be put in a hole in the garden or added to your compost.