My struggles with Queensland Fruit Fly in my apples and tomatoes got me thinking. How do they control the little blighters commercially?
So I did some reading, and I’m deeply uncomfortable with the results.
I’m not a scientist, and I know that it is easy to get the heebie-jeebies about things that sound scary because you don’t understand them. I was trying to keep an open mind.
But here’s what I found:
Up until September 2011, tomatoes in fruit fly affected areas of Australia (including Bowen, Bundaberg and South-East Queensland) were sprayed several times during the season with the insecticide dimethoate (also known as Rogor and Lebaycid). They were also dipped post-harvest in the chemical to kill any remaining fruit fly inside the tomatoes. I believe that this was mostly for export purposes, so tomatoes could be sent to New Zealand (where they don’t have fruit fly).
Dimethoate is a systemic insecticide. That is, it is absorbed by the plant and affects the plant tissue. The buggies bite the plant and die, so it’s really affective, but worryingly, it cannot be washed off.
In September 2011 it was determined that the levels of dimethoate could exceed the levels that were considered safe. The Australian Pesticides and Veterinary Medicines Authority (APVMA) therefore suspended its use in tomato (and many other food crops). It is still allowed to be used pre-harvest before fruit set for fresh tomatoes, and pre-harvest with a 21 day withholding period on tomatoes for processing.
My concern is : Why was this chemical OK last year and under a cloud of suspicion now? I understand that this suspension is a measure of caution and that a large margin of safety is built into the recommended public health standard, but seriously (now I’m losing my composure) why were we eating tomatoes dipped in toxic stuff that will kill a bug on the INSIDE?
References :
http://www.apvma.gov.au/products/review/current/dimethoate_faq.php
http://www.rirdc.gov.au/programs/established-rural-industries/pollination/tomatoes.cfm
500m2 in Sydney 
Ugh, systemic pesticides in vegetables, what a horror! I don’t trust the standards for what is considered a “safe” level of pesticides in food. They don’t study the cumulative effects of ingesting “safe” levels of poison over long periods of time. I’m with you, organic is best and home grown is better. Good luck with your fruit fly battles.
I agree, those systemic pesticides are totally dodgy.
There are organic fruit fly controls based on a naturally occurring bacteria (Spinosad), but like all organic pest controls they need to be reapplied regularly, especially after rain. I’ve used eco-naturalure (it’s based on Spinosad) and it’s a bit of a hassle to mix up and apply, but it worked fairly well. Yates Success isn’t designed for controlling fruit flies, but it is based on Spinosad too and isn’t toxic to people or bees, and several gardeners say they’ve noticed that spraying with Success to control caterpillars seemed to have an effect on fruit flies at the same time.
Thanks for visiting my blog Jamie. started using Eco Naturalure this year. Hopefully I’ll have some success with it too.
Yuck! In your searching, did you find any information about how organic farms control fruit flies on a large scale?
I believe that they use a mixture of spinosad (naturally derived and not applied to fruit), exclusion (nets etc) and a few other methods like kaolin clay.
It amazes me that we would use chemicals on anything that we were going to put inside us.
Yes – people seem to accept it so thoughtlessly too. How do you control fruit fly in your tomatoes at Purple Pear, Kate?