Glyphosate: War of the Weedkiller?

weed matting with pineapples

Weed mat avoids the need for weed control amongst a pineapple crop. It also helps cool soil and conserve moisture. Cook Islands.


Letter to Graham Readfearn, a Brisbane-based journalist at The Guardian Australia concerning his recent article about glyphosate, the world’s favourite herbicide.


Dear Graham,

Thank you for your article, ‘War of the weedkiller’. It is a good read.

I wish it had highlighted the two different positions, that of conservationists and of environmentalists, in the way they happily co-exist rather than as if they are conflicted.

First up, sustainability involves diverse people, it includes many shades of green.  Broadly, a conservationist has a primary focus on species and habitat biodiversity, while an environmentalist focuses on the total environment, and includes global issues such as the health of the air we breathe, the water we drink and the food we eat.

1) The conservationist view is that the precision use of glyphosate is useful for habitat restoration: limited applications in a limited area (Tim Low’s point in your article);

2) The environmentalist view that poorly researched pesticides threaten human, animal and environmental health, and especially so where they are used frequently and at a landscape level (Jane Bremner’s point in your article);

I agree with Jane Bremner of the National Toxics Network Inc. that glyphosate presents health hazards. Research has found glyphosate to be a bee-killing pollutant of groundwater, rivers and surface water, and it is helping bacteria become antibiotic resistant.

The strength of her argument rests on the frequency and quantity of application at a whole of landscape level on farms, near rivers, oceans, directly on aquatic weeds and roadside weeds, street tree and park weeds across towns and cities.

Glyphosate is the primary chemical used as a broad scale desiccant, it is used to speed up crop ripening for harvest. It is applied directly on floating aquatic weeds, such as hyacinth weed, in major rivers (like the Brisbane River catchment) and waterways. As glyphosate molecules denature in water, it is responsible for pollution – each molecule releases a nitrate molecule as it degrades, fuelling algal blooms which in turn affect the health of waterways (especially during drought) and the health of inshore reefs and marine life, including seafood.

I agree with Tim Low’s conservationist argument that glyphosate, used as a precision tool in securing areas of natural biodiversity threatened by weeds, is invaluable. A few, targeted applications in remote, or heavily infested bushland, or difficult to access bushland sites can save thousands of hours of manual labour, and it can avoid disturbing the soil during the process of manual weeding which avoids bringing more weed seeds to the surface. This saves a lot of money, time and effort. 

The hazard of glyphosate to human health increases with the risk of exposure taken: there is a difference in risk if you are employed as a spray operative in the field, or a pedestrian walking your dog in a suburb. Risk varies according to the scale and the frequency of chemical use. There is a greater, direct risk to operatives who regularly mix chemical concentrates and apply them than there is to people going about their daily routines in parks, gardens, streets that have been sprayed with chemicals; and there is also indirect risk through exposure in the food supply sourced from land  and sea.

A common concern

What unites conservationists and environmentalists is the knowledge that, should glyphosate be withdrawn, alternative or substitute herbicides, such as dicamba, mecoprop, MCPA, 2,4-D, etc, are more volatile at ambient temperatures (and therefore more difficult to contain) and more hazardous to the user and consumer.

Your article is excellent because it highlights the difficult and sometimes emotional conflict amongst conservationists and environmentalists. But it didn’t highlight the point  that conservationists and environmentalists agree on – we should reduce the scale and frequency of use of chemicals, and we should reduce exposure to chemical hazards for humans, animals and the environment.

slashing roadside weeds, Fjaerland, Norway
Here also grow wildflowers: No poisons needed to slash roadside weeds. Fjaerland, Norway.


Environmentalists and sustainable farmers are united

No poisons are needed to slash roadside weeds. Fjaerland, Norway.

What unites environmentalists and sustainable farmers is that farming was capable of producing good food for the masses long before the advent of glyphosate, and it can continue to do so in the future.

There exist other, well established and successful methods of weed control at a landscape level. Mechanical control is one effective method of control familiar to anyone who has seen a lawn being mowed and edged. Norway does a good job slashing roadside and kerbside and street tree base weeds on a national scale. Many techniques existed well before Monsanto-Bayer were formed to make money from chemicals. These techniques are effective, economical and safe. 

If there is a ‘War of Chemicals’, the biggest chemical story is hiding in full view. How do the tens of thousands of registered chemicals in everyday use receive their approval for use in Australia? Why does the Australian Pesticides and Veterinary Medicines Authority (APVMA) give its approval  without full, considered knowledge of their wider impact to the environment? Why does the APVMA refuse to apply the precautionary principle in its regulatory process? Why does the APVMA delay the review of hundreds of chemicals approved by it when their true nature and impact is revealed by independent research? The irony here is that sometimes even the APVMA decides to review chemicals it has approved following scientific evidence and when it does the progress is glacial: in 1996 the APVMA started its own review of the toxic pesticide chlorpyrifos, it took 22 years to conclude, meanwhile this known-to-be-dodgy chemical was in widespread, everyday use in home gardens and farms! Just one of tens of thousands of chemicals it has approved for use in Australia.

Just why is the APVMA marketed to the general public as being ‘impartial’ when its work is funded from the profits made from the sale of pesticides?

Hiding in full view is the myth that, with regards to chemical approvals, chemical use and human exposure, children are regarded as merely small adults. Nothing could be less scientifically accurate or further from the truth. 

Thanks for a stimulating article. Love your work.

Kind regards,

Jerry Coleby-Williams RHS, Dip. Hort. (Kew), NEBSM
Patron, National Toxics Network Inc. – ‘The Voice of Reason’
Web: www.ntn.org.au

26th November 2020

6 Comments Add yours

  1. Janet Iffinger says:

    Hi Jerry,

    Congratulations on the very well written and researched article of reply.

    Kind regards,

    Janet Iffinger

  2. Stephen Besnard says:

    Very interesting

  3. Roma Harris says:

    Your letter made me think deeply about using glyphosate on my garden weeds. I have used it sparingly in the recent past in addition to grubbing out. Yesterday I used a contact weed killer called Slasher which worked in a few hours and I was able to grub it out in between my pavers. Hard on my old knees though. I’m thinking of making a homemade contact killer using vinegar and salt which I think I saw on ABC Gardening Australia.

  4. Denise Barber says:

    Thank you Jerry,
    I really appreciate your articles and the insight you always give with your wealth of knowledge Thank you

  5. Linda Edwards says:

    Dear Jerry
    I have used roundup on weeds that have bulbs, but they still come back. I try to watch Gardening Australia every week. Thank you, Linda Edwards.

    1. Hi Linda,

      Roundup is a systemic herbicide, which means it can spread throughout a plant above and below ground. What’s missing here is how to enhance the herbicide effect and when best to apply. Dissolve one tablespoonful of urea (bought separately from a garden centre) per litre of mix. Apply in March to May. Urea accelerates cell division, enhancing the impact of roundup. Autumn application coincides with the time when bulbs store food and therefore sap flow helps to transport the herbicide into the bulb.

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