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September 30, 2016 Archives

A couple of days ago I did a spot of live radio with the good folks at 95bFM. It was great fun. One of the topics was dog evolution, which I've already written about here; another was the recent publications on human dispersal, covered nicely over on

The third was a brief discussion of claims made in an article on stuff, in relation to organic farming & its use of pesticides & insecticides. More specifically, the writer (Dr Libby Weaver) said this (my emphasis):

Organic produce is labelled "certified organic" when it has been grown, raised, harvested and packaged without the use of pesticides, insecticides, growth hormones and antibiotics.

Now, that phrase I've emphasised is simply incorrect, and extremely easy to check (as was pointed out fairly emphatically by several commenters on the original article). It would have been correct had the statement included something like 'synthetic' pesticides & insecticides, because organic farming certainly uses chemicals to control pests. Copper sulphate, for example, is widely used as a fungicide, while rotenone & pyrethrum are common insecticdes. 

There's an interesting post on organic production here. It comments, rightly, that many of the chemicals used in organic production in the US are quite toxic - and then goes on to point out that this need not be a problem if they are used correctly because it's the dose that makes the poison - something that is true for both organic and conventional farming.

But I snuck 'biodynamic' into the title of this post, & here's why. In that same stuff article we find this statement: 

it is so important to support organic, biodynamic and sustainable agricutlure.

I doubt anyone will quibble over the need for farming practices - whether organic or conventional - to also be sustainable.

But 'biodynamic'? Here's an NZ website about biodynamics; it did make me wonder how familiar the OP writer was with its contents. For instance, biodynamic practice appears to include the belief that the stars & planets have an influence on crop production - but with the disclaimer that this involves astrology. It would be very interesting to see the scientific data that demonstrates an actual positive impact from the stars on plant and animal health & production. (Note: the actual stars - not regular seasonal changes.) There's some interesting commentary on biodynamics here. And then, of course, there's the implausibility of possum peppering...


Incidentally, I was interested to discover that the Bt toxin, produced by a common soil bacterium (Bacillus thuringiensishas been available as a spray-on insecticide for organic farming, in some jurisdictions, for at least 50 years, and is used in New Zealand. Arguments in favour of this, and against the use of GM crops that express the same toxin, include the suggestion that the latter could lead to widespread resistance to Bt toxin. However, the use of targeted sprays is also an agent of natural selection, & could eventually have the same result.

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