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



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).

Pesticides that kill bees

Neonicotinoids kill bees

There is a major class of pesticides  - Neonicotinoids - that is known to kill bees. This is a HUGE problem in the United States, where last year beekeepers lost 42% of honey bee colonies, and neonicotinoids are thought to play an important part in that loss.

One pest control company in the states Ortho, has just announced that they are going to "immediately transition away from the use of neonicotinoid-based pesticides".

Read the whole Huffington post article here including some great links to further resources.

And Wikipedia states that "The neonicotinoid family includes acetamipridclothianidinimidaclopridnitenpyramnithiazinethiacloprid and thiamethoxam. Imidacloprid is the most widely used insecticide in the world."

And it also provides this handy list of which products contain them (this is 2011 data)

NameCompanyProductsTurnover in million US$ (2009)
ImidaclopridBayer CropScienceConfidor, Admire, Gaucho, Advocate1,091
ThiamethoxamSyngentaActara, Platinum, Cruiser627
ClothianidinSumitomo Chemical/Bayer CropSciencePoncho, Dantosu, Dantop439
AcetamipridNippon SodaMospilan, Assail, ChipcoTristar276
ThiaclopridBayer CropScienceCalypso112
DinotefuranMitsui ChemicalsStarkle, Safari, Venom79
NitenpyramSumitomo ChemicalCapstar, Guardian8

We do have our own rules governing the use of neonicotinoids, from the EPA, read about them here. But they basically say you're not to spray near beehives or on flowering plants. So they haven't been banned at all.

Neonicotinoids are used to coat some seeds, and these are still sold in NZ.

Two products available in NZ that contain neonicotinoids are "Yates Confidor" and "Yates Rose Gun Advanced".

Also "They are sold here under the common trade names of Cruiser, Gaucho and Poncho, the active neonicotinoid ingredients of which are thiamethoxam, imidacloprid and clothianidin respectively. Gaucho is also used on potatoes, winter squash and pumpkins."

And from Apicare NZ:

Why neonicotinoids are bad for bees

There has been much talk about this group of insecticides globally.  There are now bans and trial bans in place in many areas around the world.  This is not so in New Zealand, so we need to keep a particular eye out for the ingredients we spray in our gardens and on our farms.  Neonicotinoids work as an insecticide by blocking specific neural pathways in insects’ central nervous systems.  At ‘sub-lethal doses’ the chemicals impair bees’ communication, homing and foraging ability, flight activity, ability to discriminate by smell, learning, and immune systems – all of which have an impact on bees' ability to survive.  Neonicotinoid pesticides have been linked to the dramatic collapse in bee numbers over the last decade.
Domestic Sprays that contain neonicotinoids - Many domestic gardening products on sale in hardware stores and garden centers contain these chemicals.  If you're buying any kind of pest control check the ingredients – anything that contains acetamipridimidaclopridthiacloprid or thiamethoxam should be avoided to maximise bee health.
While the topic of bee safe sprays is relevant topic it is also one that can also be rather confusing. There are so many different garden sprays available in the market place and so many different chemical names, brand names and generic names that making a considered choice can seem impossible. We have tried to simply the issue below by providing some brand names commonly available in the New Zealand market place.
  • There is evidence overseas that the use of a group of pesticides known as neonicotinoids cause bees to become disorientated when out foraging and may be a major contributor to the phenomenon of Colony Collapse Disorder which is decimating bee populations in Europe and North America. Neonicotinoids have also been shown to cause chronic bee mortality through reduced immunity.
  • Bees do not have to come in direct contact with the spray residue, they can absorb the neuro-toxins via the plants pollen and nectar.
  • The common names for neonicotinoid insecticides are Acetamiprid, Clothianidin, Imidacloprid and Thiamethoxam.
  • Neonicotinoids are often used for agricultural applications but can also be available to the home gardener. The two products that New Zealand gardeners are likely to come across (containing Imidacloprid) are Yates Confidor and Yates Rose Gun.
  • It is not just neonicotinords that can be harmful to bees. Other common pesticides that are toxic to them include insecticides containing Acephate, Carbaryl, Spectracide, Permethrin and the rapid flying insect killer Resmethrin, to name a few. Ther is an extensive list on Wikipedia under pesticide toxicity to bees.
  • Sprays that are safe to bees if sprayed at dusk when the bees won’t be foraging for a number of hours (i.e. they are safe to bees as long as they are dry and no longer wet): Spinosad (Yates Success Naturalyte Insect Control), Yates Guardall, Yates Mavrik Insect & Mite Spray, Pyrethrum (Yates Nature's Way Fruit & Vegie Gun, Yates Insect Gun Ready to Use, Yates Natures Way Pyrethrum, and Neem Oil.
  • Sprays that are safe to bees (though it would still be best to spray them at dawn or dusk when bees aren’t flying): Sulfur, Serenade, Insecticidal Soap Based Sprays (Yates Nature's Way Insect & Mite Spray and Yates Mite Killer), Petroleum based oils (Yares Conqueror Spraying Oil), B.T. (bacillus thuringiensis), Herbicides (like round-up).
So if you are at all interested in the survival of honey bees, please DO NOT USE any of these toxic chemicals.

Others are bad too, although not as dire, and in the next post I'll outline how I research these things properly and how you can find out what ingredients are suspect, rather than just relying on the supplier saying it is "not toxic to bees".