Effectiveness and ethics of using herbicide on invasive species

Ok this is a bit of a story but it is surrounding an issue that has been troubling me that I have had issues finding information on. So I served in the conservation corps this past year working in a natural resource management crew for state parks. A big part of the job was managing invasive species in the parks. The problem is that the main strategy for dealing with this is herbicide, most commonly Glyphosate. So I spent all spring and summer spraying herbicide on invasive plants in state parks, and I don’t mean a little squirt bottle worth at a time, I mean hundreds of gallons overall. Where this story gets worse is that it’s not solving the problem. So theoretically if I managed to kill all of the invasive species in the park, (I know I didn’t because I was the only crew member working in the district in a more developed region of the state so sadly invasive species were just as prevalent as the native ones) the next spring they would come back just as strong because these species are everywhere surrounding the parks. So the end result is every year an obscene amount of herbicide is used to kill these plants just so they could all spread back into the park to sprayed again next year (it also doesn’t help that the department of transportation is actively planting these invasive species all over the state for erosion control). So overall the only outcome of this is dumping tons of toxic chemicals on plants and into the soil to not solve the problem. The companies that produce these chemicals claim that they go inert over time, but they also claim that roundup aka Glyphosate doesn’t give you cancer. I am struggling to find information regarding the effects and efficacy of this strategy. I also feel horribly guilty for all of the herbicide I have sprayed because I know firsthand how toxic and widely used this stuff is. The state parks extremely liberal use of these chemicals is shocking and I can’t see how it is not having serious negative effects. Is this an effective way to deal with invasive species? Is spraying poison everywhere really better than having invasive plants? Does anyone know why it is used so abundantly by government agencies? Is there a profit motive? The park system is horribly underfunded and is dependent on volunteers and prison labor because they can’t afford to retain or hire staff so I can see the argument being made that it is more efficient than removing it manually but is it worth the collateral damage? What are the long term effects of this heavy and sustained use of herbicide? Did I actually make a positive difference or did I just make Monsanto a healthy profit by pointless spraying poison all over state parks and made the health of these environments even worse? For me at least a more secondary concern is that is this method ethical and effective enough to warrant exposing myself to these chemicals which are taking years off my life and have serious medical consequences? Please help!!!


As much herbicide as it seems you used they probably dump more on one round up ready cornfield in a year than California state parks has used since they existed. Invasives are a hard one because they are nearly impossible to get rid of but not doing so also causes horrible problems. There are some odd pro invasive species types out there but overall, it’s a complex problem with complex answers. I used to work on a crew spraying invasive species with round up in California also. Do I feel guilty about it? Not at all. Bigger issues with inappropriate and poorly planned and implemented restoration plantings anyhow.
My understanding is roundup is barely if at all a carcinogen. I wouldn’t bathe in the stuff. But california also labels wood smoke, sand , etc as carcinogens. Technically true yes but in reality who cares. I grew up in LA in the 80s and if I get cancer it’ll be smog not round up that got me.


The problem with Glyphosat is that it is not specific. Yes, it kills invasive species. But it also kills wild species. So actually bringing out Glyphosate in higher doses has negative effect on local wild plants as well. Usually this is not good because in this case we get rid of the one thing that is slowing down invasive pests: healthy local wildlife.
The health issue is an entirely different story. From what I gather Monsanto and Glyphosat reminds me of General Motors and lead back in the day. “Of course it is absolutely harmless, see all those unprejudiced studies by scientists who are paid an obscene amount of money by us.” There is indication of health risks, but to get that sorted out you’d have to work against an all powerful lobby who does not want anyone to point out anything that might be negative about their product.
As Charlie pointed out, pest control is a hard one. Agreed. It is especially hard because governments seek for the simple solution (“use herbicide and done.”) while there is so much work to do that they wouldn’t pay for. So we have the global situation as you described it: kill 'em by poison, and then watch them return next year, repeat.
A typical story that happened to relatives: uncle uses Glyphosate to get rid of garden pests, and kills the priced rose bushes of auntie. Rose bushes remain dead, garden pests returned next year even stronger …


I’ll preface this with that I work in environmental conservation, and opinions can be divided, especially between people working in the field and people who support environmental conservation but who don’t actually work in the field. That’s not a statement about who is right or wrong, but perspectives can differ quite a bit when the actual practicalities come into play.

My opinion is that herbicides can be extremely effective, but use has to be carefully evaluated in advance and the approach tailored to the specific situation. As a general rule I don’t think spraying is a good approach. I prefer the cut-and-dab method. This is more for woody plants, not herbaceous ones. It involves cutting the stem and applying herbicide directly to the freshly cut stem. This is highly effective and is targeted to the specific plant. It’s far faster than trying to weed wrench roots out, and also can (not always) prevent root fragments from growing into new plants).

In areas where there is a dense layer of non-native growth, especially herbaceous growth, I can see the appeal and use of sprays. In those cases I’d suggest that there are certain things to be avoided: not during rainy season, not near permanent water, not during peak animal feeding times, etc. Also, that the type of soil should be considered.

People love to have clear-cut answers that lay out a strict this/that divide, but in real life this is rarely the case.

In one situation one approach (eg. herbicides) may be appropriate, in another situation something different (eg. livestock) may be effective and appropriate, in another something else (eg. hand pulling, mulching, etc). It’s not a 100% clear-cut answer, and the appropriate approach should be tailored to the specific situation. At least in the ideal world.


I don’t know what ground you work in, but I have experience in feilds where we grow crops. We don’t use herbicide, we first grow crops and then we cover it soil with something organic like dried leaf and, one thing we keep in mind is that we don’t overuse fertilizers, but I think its the park we talk about where only one type of grass of grown, so manual pulling is the best, as they will soon become immune to herbicide, and also its big company, who make inefficient fertilizers and herbicides so that farmers take more and more.
So I guess if possible you should sort out this problem with your authority to provide more labour and effective tools, nothing else can help you


I also wanted to add that in an ideal world, i could see management of inavsive plants as totally viable - not eradication, but management to make them ‘behave’ and particupate in the ecosystem instead of acting like cancers or viruses. Most land areas on the globe were once managed in a participatory and very detailed way by indigenous people. One can argue specific cases and yes sometimes indigenous groups also crashed the ecosystems and had famines, etc, but as a whole, our species is meant to have a close relationship to ecosystems. We can be destroyers, but we can and often are also tenders and tweakers. It’s part of why our brains got so big. If we adopted that same approach again in terms of native ecosystems we could restore most any native ecosystem and keep invasives from being a problem in many if not most cases. But that involves an entire restructuring of society, culture, etc. While i’d argue that we should in fact do it, i don’t think we will on a large scale. I know this touches on a bunch of cultural issues too but of course it does, everything does. Herbicides are at best a low-resource desperate ploy, but i still think oftentimes it is preferable to the alternative, which is nothing. Especially in the case of early detection of new infestations, or protecting small isolated discrete ecosystems, like the islands that were mentioned above.


Welcome to the Forum!
I just add this to what has been said above. Repetitive spraying of any pesticide increases the chance of resistance developing in the target species. As @charlie said, Roundup Ready corn etc. is being used in huge amounts. It’s taken a while, but some weeds have developed resistance to it, which is causing a huge problem. At some point in the 1960’s cotton insect pests in the US had become resistant to all registered pesticides due to ‘calendar spraying’. So while the park service is using a non effective weed removal strategy, it is also increasing the chance that pesticide resistance will develop in the wider population outside of the park. People never seem to learn.
Try not to feel guilty about it. An easy thing to say, but it’s not your fault. As for the health issues, if you were wearing protective equipment the risk will be much lower. It might be worth talking to a Physician about your health concerns, though. I don’t think many of us on the Forum are doctors! Although I did work as an Intensive Care Nurse for a decade or so I don’t feel qualified to be able to offer any medical advice beyond what I have.

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this is such an enormously complex issue that it’s important to try to avoid getting bogged down in idealism. I did invasive plant control for awhile, as well.

invasive species cause big problems. they can crowd out native species, resulting in loss of diversity and other cascading effects on the ecosystem. some can change soil chemistry and fire regimes. some have resulted in the extinction of already imperiled species. the benefits of species diversity are pretty wide-ranging.

some can be massively expensive to deal with. Sure, in an ideal world, addressing invasives wouldn’t involve chemicals at all. But honestly, what else are you going to do? I use very few chemicals at home (I do use some, sometimes), and dealing with unwanted plants (not all are nonnative or invasive - they’re just growing where I don’t want them) is a lot of stinking work for half an acre. Scale that up to large park level (thought experiment time!). How many people do you think it might take to work over an area?

Biological control is massively more efficient - when it works. You have to be incredibly careful that you don’t release something into the ecosystem that’s going to cause more problems than the thing you’re trying to address. That mistake has been made more than once, so we have an idea about the implications for f*cking that up.

There’s definitely a school of thought out there that it’s just not worth the costs to do anything about invasive species. Part of the argument there is related to the concerns you’re expressing here. Another part of it is that species have always moved around the planet. More mobile species moreso than others. Take the nine-banded armadillo as an example of a species making large movements on its own. When species move to a new place, they do make changes to that ecosystem. That’s how it works. By deciding to remove certain species, we’ve made a human judgement about things. Not necessarily an ecological one.

I see both sides of this. If an organism or a habitat is imperiled, I think it’s worthwhile to protect it at great cost. Humans have made lots of changes (both intentional and inadvertent) and many are resulting in a loss of species diversity. All of those species have value, so I think it’s worthwhile to protect them. That said, I think once a species establishes itself enough to become “invasive”, there’s really no practical way to eradicate it unless we’re talking about fairly small enclaves. And even then, eradicating it might have be more costly (money is only one “cost” in this context) than it’s worth. Shoot, there are even some cases where certain species are invasive in one place and imperiled in their “native” range. So for some species, there might even be some conservation value to being relocated. How to fit that scenario in with all the others?

That said, I think we should probably shift some of our expenditures from dealing with invasive species that are already present to preventing species from becoming established as a result of our own actions. The garden industry is responsible for a great deal of invasives around the world. The pet and aquarium industries, as well. Shipping is another one, but I think that one is a little more difficult to get a handle on.

All in all, addressing this takes a pretty nuanced approach. Taking the position of “chemicals are bad” ignores a massive amount of that nuance.


Around Cape Town the most invasive plants I am aware of are Australian wattles. Felled and left in stacks for burning later. Tiny ones pulled. Stumps are treated with herbicide.

To respond to @grey_wolf I read a blog. She does an annual stint in a national park. Hand-pulling weeds. Absolutely no poison involved.
Weeding in Yellowstone

I agree with you, unfortunately my HOA uses Roundup although I have asked the President of the board if the ground crew could stop using it. I carefully planted spring bulbs around a tree in a circle of mulch and early winter when the Persian Buttercups came up they didn’t have a chance. Someone diligently sprayed each plant—never mind that weeds rarely grow in such a well-spaced circular pattern.
Also there is a weedy, uneven hillside I’ve been working on improving at the edge of my complex. I planted a few small hydrangea bushes but at the time I couldn’t afford much mulch so weeds grew near them. Unfortunately the grounds crew was thorough and came and Rounded up that area too. Using poison to kill weeds on an already eroding hillside wasn’t smart. It would have been a real problem if poison ivy, morning glory, brambles and muscadine hadn’t come to the rescue. Who needs irises, Persian buttercups, and hydrangeas anyway?


Here’s a related article that I ran across a few weeks ago. It’s perhaps a valid perspective to be very selective in our battles against exotic species–and not just because of potential negative impacts of herbicide.
Don’t judge species on their origins

My two-acre property, which I had hoped to maximize native plant diversity for pollinators and other insects, is rapidly being taken over by King Ranch Bluestem (which creates a monoculture–eliminating all plant diversity). At first, I was going to try to keep it at bay. But the entire state is being taken over by it. So I decided that my time would be wasted in any effort to keep it off my property. Even if I could control it with herbicide or other means, the moment I ceased my efforts due to old age or death, it would take over in 2-3 years. So what would be the point.


I don’t feel like use the way the park service does it will cause resistance to develop. I’m talking about agricultural use.

Also I feel like people do judge species by their impacts more than their place of origin. I als o feel like the word judge anthropomorphizes too much. It’s not a human in court. It’s a plant species or an insect. It either is invasive or isnt.


The LD50 is a great place to start when looking at how ‘toxic’ something is, the amount that would kill 50% of people who ingest that level (lethal dose, 50%) Roundup is really safe in this sense for sure, better to much better than the vast majority “organic herbicides”.

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You can calculate the amount used and determine just how much you are using, because it probably is not anywhere near as much as it seems.

If you have particular species you are trying to get under control, maybe try doing what the land trust did near here for privet: set up some test plots. They set up up the following:

  1. control, nothing done
  2. Hand pulling the privet (weeding)
  3. Glycophosphate
  4. Hand pulling + spray any stumps not able to pull with glycophosphate

Hand pulling + spray is still good now like 5 years later, then just hand pulling, and then only glycophosphate which is almost as bad as the control now. of course a this point all the small test plots are suffering from encroachment.

So if you have time year-wise, maybe set up such test plots? And there are other herbicides than glycophosphate like triclyopr which may work better, could add more test plots.

Also make sure the mix is to the correct concentration, as for the example I am familiar with, off the shelf mixed are usually not to the concentration needed for privet. And you spray it on the leaves on non-windy days making sure full plant coverage. Done right, it does work. the plant dies. But the root system can pretty easily survive and sprout off, which is why manual pulling making sure to get the root system works best, and if you can’t get it pulled out, cut off and the stub left drenched to get it into the roots and stop resprouting. And why by year 2 the privet was already starting to take back over in the ‘spray only’ test plot.

TLDR: one size does not fit all for invasive management, and making sure you are doing the right technique/mix of technique for the exact invasive you are after is the important thing or you will end up doing the same thing year after year…which if it isn’t working, then nope it isn’t effective management is it?

As for being exposed to it, i’d be 99.8%+ sure you are fine but frankly anything tends to upset my nose, so whenever I’m spraying anything at all I wear a mask so I don’t inhale any blowback if there is a gust of wind. Heck the amount of chlorine in our local tap means I sometimes wear a mask hosing off dirty gear outside so I know I’m sensitive! But yeah, you likely get more cancer-causing-fumes pumping your gas than that, or much else in your life (my ochem professor in college studied cancer and loved giving us those numbers to show how weird people can get about things, and yet ignore things that are actually far worse - but still not bad at all in the span of life we live!)

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If it was me, I would have carefully documented it and reported it as vandalism.


Thanks for the empathy. However, I’m convinced it was a bad case of “winter annualitis”. Not malice, but ignorance which motivated the destruction. For the average plant-blind lawn crew the only good winter annual is a dead winter annual. Persian buttercups have broad leaves rather than blades. :anguished: Broad leaves bad, blades good. At least the current yard crew has stopped chopping off my patch of irises since I put an ornamental stepping stone by them. I am saving a stand of goldenrod and some American wild asters by marking out an area with bricks and mulch.


I recognize that. I was simply adding one more factor to consider with any routine pesticide use. I don’t know which weed is being targeted and how easily it may develop resistance.

While LD 50 is a good measurement of toxicity to humans, it says nothing about the overall environmental impacts. DDT has a very high LD 50, yet its wider environmental impact, as we know, has been significant. Glyphosate is very different, of course - my understanding is that it breaks down very quickly, as do most modern pesticides. It is the longer term effects that take a while to show up, both in people and in the environment. When I want to know the side effects of a drug, I always start with the after-market list. Weird side effects often show up after time. Perhaps it’s taken this long for the cancerous effects of Glyphosate to show up. I really don’t know much about the substance.
And, for the record, I’m not fervently anti-pesticide or anti medication. They have their place, but are often used when they do not do need to be. Personally, I’m more concerned about antibiotic resistance than I am about pesticide use.


Santa Clara Valley Open Space Authority has used both cows and goats on the open space preserves for non-native grass control. The Santa Clara Valley Water District also hires goat herds for selected properties. I’ve seen East Bay Parks (Alameda County) use goats in some of the meadow areas and hillsides.

I’m seeing goats used more often on such parkland-like spaces for weed control and fire prevention. I cannot say if it is more effective for native plant preservation, but it does seem like a good alternative to poison.


Oh and we have the Gantouw Project using eland. LARGE animals can tackle invasives and the shrubs that are too vigorous and need to be burned - but - not in natural areas with houses nearby.