Wednesday, 8 October 2014

About Fruit Fly Exclusion bags

Here in Perth we have Mediterranean fruit fly. These little @*^%$s (excuse the language) make the stone fruit growers life a disappointing one. I’ve had a few years of battling with these critters so let me give you the benefit of the vast wealth of knowledge I have gained (ahem).

First up, let me just say that if you think you’re going to protect your fruit by hanging old soft drink bottles with a mix of vegemite and ammonia in your trees, think again. I tried this the first year and lost all of my fruit. I still use this system but only to kill as many as I can catch.

The second year I whipped myself up some fruit fly exclusion bags out of fine netting. The first ones were made out of bridal veil (expensive), then I moved onto mosquito netting (this was black and I like to be able to see if the fruit is ripe), then a coarse netting (cheap but too stiff to manoeuvre) and now I’m using cheap net curtain fabric (this works the best of the lot). You can actually buy exclusion bags if you’re not able to make them. These work! But there are some things you should know:

1.    You will need to double them because if the net touches the fruit the fruit fly will be able to get through it. Don’t go thinking that a shortcut would be to double the layer of netting on your bags (I tried that in years 3 and 4). The layers need to be independent so that there is some air space between them.

2.    You will need to put them on early, once the fruit has some decent size. Fruit flies seem to particularly like apricots and, because they develop in size quickly, apricots are the crop that sometimes gets away from me. Usually I spot fruit fly hovering around the fruit and then panic. Not this year though, and I’m looking forward to some good fruit.

3.    Other critters like ants, ladybirds and cockroaches (ick!) will still be able to get in and you’ll see them roaming about in there. I don’t quite get why this is but there we are.

I use pegs to attach the bags to the tree. For smaller fruit like apricots and plums I use a larger bag and enclose several within it, for peaches and nectarines I bag single fruit. Because this takes time, I decide how much fruit I’m likely to eat over the time that the fruit will be ripening (I calculate this to a 2 week period although it’s probably longer) and I have enough bags to cover this. This doesn’t leave any to hand out to friends, neighbours and workmates. The whole time I’m bagging fruit I’m thinking of the story of The Little Red Hen  ;-).

Once the fruit is bagged, I strip the rest of the fruit from the tree. It’s a heartbreaking task but not as heartbreaking and messy as getting rid of rotten fruit fly infected fruit (I put them in a plastic bag and leave them in the sun for a few days to kill the maggots, although I believe you can feed them to chooks if you have them). By the way, other states of Australia have rules that require reporting of fruit fly, so please check.

Finally, I’ve succeeded in growing figs with only minimal fruit fly problems, especially at the start of the season. Perhaps this is because the fruit is hard and then softens quickly when ripe. Anyway, if they’ve been on the tree for a while I’ll let them go and the birds will eat them, and I always check for fruit fly before eating. I’ve also had mixed results with the plums so I will still leave the unbagged fruit on the tree for these fruits. Last year the unbagged fruit survived, but I have, in the past, lost the whole crop as well, so I wouldn’t want to leave it all unbagged.

Oh, and before I forget! The blood plums don’t colour as normal, although they still ripen. Perhaps the bloom is being rubbed off them or something. Anyway it’s quite a mystery and I need to experiment a little more with them.

Happy Gardening!

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