Weed killers and bees

How to tell if a weed killer is toxic to bees

Google is a great thing, but also those 2 hours you spend researching something, you never get back, right? I've done quite a bit of research into specific weed killers for our hosts, and thought I would share the better websites that I have found on the way.

Caveat: there isn't AN answer. You can believe what the manufacturers say, or the 'never ever use weedkillers' crowd, or the 'only true if it has been proven by science' crowd - the problem with this last one is that there hasn't to date been a lot of research around all this, bees just got on and did their thing and nobody worried. But now with big problems with Colony Collapse Disorder, especially in the states, more attention is being given to this issue. But any good science takes years, and even then might not produce a definitive answer.

That being said, here is what I came up with:

Say you are going to investigate Conquest.

Its supplied by Nufarm, so if you google it you get the Brochure. Doesn't say what is in it though.



What you want is the label



which lists the active ingredients



picloram and triclopyr in this case.

So let's take Triclopyr - as the butoxyethyl ester:

 (picloram, by the way, was used to make Agent White, and enhanced Agent Orange during the Vietnam War - just saying!)

So on Wikipedia, doesn't say much except that it is "chemically very similar to the herbicide which it generally replaces, 2,4,5-T, which was phased out in the U.S. in the 1970s amid toxicity concerns".

Toxipedia doesn't say much about bees and triclopyr. Although Toxipedia can be quite useful for some chemicals, just not this one. (and Picloram doesn't even get a listing - depends what weed killer you are using as to what information is around).

And then Pesticideinfo which has a whole bunch of science-y information (which both my mother and brother, being chemists, would get all excited about, but the rest of us...not so much).

But down in the Terrestrial Ecotoxicity it does mention bees.



Which might be too tiny to read on this blog, but what it says is it is 'slightly toxic to bees'. And that
"Population-level effects on honeybees may occur even if a pesticide has low acute toxicity. For example, certain pesticides interfere with honeybee reproduction, ability to navigate, or temperature regulation, any of which can have an effect on long-term survival of honeybee colonies. The neonicotinoids, pyrethroids and keto-enol pesticides are some types of pesticides causing one or more of these effects".

So all up, doesn't look dire. Not great either. And I think I would take the bees away before spraying this around. And wait at least the half-life time before bringing the bees back, probably twice the half-life time - which in this case is 39 days see here. So quite a while. (the half life is the time it takes for half the product to be gone, in the soil in this case).