Eggplant borer

I have eggplant borer (Leucinodes orbonalis) in my eggplants for the third year running. I have tried spraying regularly with pyrethrum this year which has reduced the rate of infestation but not eliminated it. Without spraying I get about 10% edible fruit, with spraying about 50%. I have searched the internet and it seems there is no cut and dried solution. One of the problems is that the eggs are layed by moths continuously through the growing season and the grubs are only vulnerable for a short time to contact toxins before they burrow into the fruit and vanish. I prefer not to use systemic insecticides and it isn't clear that they are completely effective either. I don't need 100% effectiveness but only 50% is too much waste for my liking.
My next method of control (next year) is to grow my eggplants in net cages to keep the moths off them. Before I go to this trouble does anybody have experience of the problem who can offer a practical solution that is better than 50%.
David
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David Hare-Scott wrote:

Maybe exclusion bags. You can buy exclusion bags, or maybe use paper bags (or make some bags from nylon fabric).
e.g. http://www.greenharvest.com.au/pestcontrol/exclusion_prod.html
Do the plants continue to flower while other fruit are growing? If so, you will presumably need bees to fertilise the flowers. Exclusion bags would allow this - net cages wouldn't.
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Tom N wrote:

That's a good idea to follow up. It is unclear to me exactly when in the cycle of flowering and fruiting the grubs enter. They seem to go into a hole they drill in the formed fruit but some sources say to look for them on wilted flowers and stalks as they attack the young flowers. I haven't seen any flower damage. So maybe once fruit sets a quick squirt of pyrethrum before bagging would do the trick.

Yes.
If
I had thought that I would have to hand pollinate, we are talking about 50 flowers not 500. But the bags are worth a go. I might do some of each and see how it turns out.
David
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