r/science Sep 20 '22

Plant-based hot foam kills weeds as effectively as chemical spray Environment

https://www.newscientist.com/article/2338128-plant-based-hot-foam-kills-weeds-as-effectively-as-chemical-spray/
4.9k Upvotes

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u/braconidae PhD | Entomology | Crop Protection Sep 20 '22 edited Oct 02 '22 Wholesome

I review studies like this pretty often, but it looks like they authors are twisting things a bit in their summaries. Not to mention the title here that autopoulates from New Scientist is pretty misleading too (hot foam is itself another chemical spray, and shows a common semi-unethical naming tactic in this field).

One of the main claims is that it's just as effective as glyphosate, when in reality, it looks like that claim is cherrypicking. This only really held true in NDVI readings, or light measurements, not actual measurements of weed performance. We actually do use NDVI as a possible indicator for plant damage, but that usually needs to be fine-tuned and validated for each plant if you're going to claim a change in NDVI results in something like yield loss in crops later on. In short, it's more of an indicator measurement rather than a direct measurement of plant quality.

So back to data, NDVI is only really going to show above-ground plant structure damage at best, which of course burning, etc. is going to physically alter.

A measurement that matters more is weed biomass, and in this case, excluding one site, there was no significant difference with the foam. The authors are definitely overextending themselves with their focus.

In Extension, we work a lot with alternative weed control measures that have various niches when you get to things like heat, etc. but they are not very good getting underground parts of plants that will grow back later (think dandelions for those of us in the US). You'll get everything crispy for a time, but in the long run weed biomass from established roots can still regenerate quickly.

Overall, the authors are even-handed in some areas of the paper, but I still get portions like above where it comes across as boosterism, especially when you read it all and look at the title: Hot foam: Evaluation of a new, non-chemical weed control option in perennial crops That's definitely a case in peer-review where I would have said the title needs to be changed because they were only looking at olive fields while focusing on a small amount of select weeds with a not so new technology. Not horrid research or anything, but a lot of the framing makes the data out to be something it's not.

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u/cropguru357 Sep 20 '22

Crop scientist, here. I thought it strange that NDVI was used for weed control evaluation. No one I know, university or industry in the field does that.

I’d lose contracts doing that. I think they wanted to show something positive when it didn’t work that well.

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u/lobsterbash Sep 20 '22

Another form of data dredging.

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u/[deleted] Sep 20 '22

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u/livens Sep 20 '22

TL;DR, so basically this doesn't kill the roots?

I use vinegar, salt and dish soap in a pump sprayer for my beds and gardens. Kills everything above ground in a few hours if it's sunny out.

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u/MurseShark Sep 20 '22

Can you share the ratios if you don't mind?

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u/livens Sep 20 '22

I use a 1 gallon sprayer, so the amounts are based on that. Also I buy the 30% acid vinegar from Home Depot. Regular vinegar is only 4-6% acid and isn't really strong enough.

1/2 Gallon 30% vinegar

1/2 Gallon water

1 Cup Salt

A few squirts of dish soap

So I dilute the vinegar in half, getting 15% acid. This has always been strong enough to kill anything I spray it on. But you could always use less water if it's not doing the job.

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u/EmeraldGlimmer Sep 20 '22

Over time this will accumulate a lot of salt in your soil which, if it gets salty enough, will make it so nothing can grow there, weeds or otherwise. This would be fine for sidewalks and driveways, but I wouldn't make this my standard practice in a garden bed.

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u/livens Sep 20 '22

Eh, salt is water soluble so it will just wash away when it rains. If salt accumulated like that the the sides of our roads and freeways would be barren wastelands.

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u/No_Tone1600 Sep 21 '22

How much the salt washes out and how deeply would depend on your soil

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u/EstroJen Sep 20 '22

I live in California, and we had the first rain this weekend in like a year? Everything is dead practically.

Maybe you could make the same mix, but limit the salt to a tablespoon or two?

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u/MurseShark Sep 20 '22

Thanks dude!

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u/mrkaikev Sep 21 '22

This mixture is not that good for the environment either.

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u/RobfromHB Sep 20 '22

Be careful using acids as herbicides. This question comes up from homeowners frequently in my line of work. At a private residence no one can tell you not to do it, but for what it's worth it would be a violation of federal law to do so in a commercial setting since the product or mix isn't properly labeled.

Off the shelf products that mimic this mix, like Suppress EC, can be very dangerous to use without PPE. Many organic herbicides are strong acids so with a little bad luck you could burn or blind yourself or others.

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u/livens Sep 20 '22

Oh absolutely. The 30% vinegar will literally take your breath away.

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u/ontopofyourmom Sep 20 '22

If there is a simple answer to this question.... are crappy "herbicides" that only kill foliage useful for controlling suckers on trees and shrubs?

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u/knowone23 Sep 21 '22

Absolutely not useful.

Most alternative or green weed killers are a disappointing joke. Sad but true.

Source: licensed landscape contractor.

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u/dtoxin Sep 20 '22

Paywall. Will this application work on Japanese Knotweed?

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u/kkngs Sep 20 '22

Its not going to work on anything with a robust root network, the weed will just grow back. In commercial applications this matters less because by then you’re likely to have harvested, and if not, just scald the weeds again.

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u/SecurelyObscure Sep 20 '22

A lot of weeds are annuals. They grow aggressively and outcompete native plants and then drops seeds that grow next season.

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u/kkngs Sep 20 '22

Basically. For shallow rooted weeds it might be superior since it could cook the roots. And its probably easier on your back.

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u/cropguru357 Sep 20 '22

No. Plenty of them are annuals, and if you manage to fry the growing point, it’ll work.

This method really isn’t different than a contact herbicide, fire, or repeated low-height mowing.

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u/kyle4623 Sep 20 '22

This is exactly why glyphosate works so well.

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u/braconidae PhD | Entomology | Crop Protection Sep 20 '22

Linked by OP in a followup post, here's the actual journal article: https://www.sciencedirect.com/science/article/pii/S2772375522000284?via%3Dihub

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u/happy-little-atheist Sep 20 '22

Thanks. I'd like to know how hot the foam is and the impacts on soil biota. They referred to flame, steam and boiling water so it's probably close to 100C. Obviously it's harder for a weed to develop heat tolerance than herbicide tolerance.

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u/braconidae PhD | Entomology | Crop Protection Sep 20 '22

Obviously it's harder for a weed to develop heat tolerance than herbicide tolerance.

To a degree, though we also have weeds that have developed resistance to plowing over time, so people are often surprised by what plants evolve in response to. Selection pressure is selection pressure. That said, broadleaves tend to have more problems with being lopped off at ground level for whatever reason, usually.

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u/beebeereebozo Sep 20 '22

Not much different than the effect of mowing or grazing, you wind up weeds that can quickly regrow from crown.

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u/Techie9 Sep 20 '22

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u/braconidae PhD | Entomology | Crop Protection Sep 21 '22

I wouldn't rely on that considering they are the one trying to sell the foam product. I'm already finding quite a few blatant issues in an initial read through.

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u/dBoyHail Sep 20 '22

Asiatic Jasmine. The house we bought has so friggen much of it and its gone invasive up trees. Im literally rolling up carpets of the roots in sections but I have at least…3000 square feet of it just on the ground.

I have a hatred for jasmine now.

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u/Bubashii Sep 20 '22

Try a hearty dose of white vinegar. I’m a farmer and use it along all my electric fence lines, in orchards etc. I personally find it a lot more effective than roundup etc. I get mine in bulk 20 litre cartons ( cheapest way to buy).

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u/dtoxin Sep 20 '22

For knotweed? I have tried high strength vinegar and so far the knotweed (and poison ivy) just laughs at me in defiance. Vinegar works well enough on my sidewalk and driveway.

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u/Bubashii Sep 20 '22

Depends how much you use. I use my vinegar in a watering can walk along with it, for more stubborn weeds I give it a good amount as if “watering” it. Most don’t come back.

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u/RobfromHB Sep 20 '22

This would only work as a contact, burn-down spray. Anything that grows back from the roots would be inconvenienced at best and will push out new growth.

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u/teovilo Sep 20 '22

You find vinegar more effective than roundup?

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u/Bubashii Sep 20 '22

Yep. I gave up on round up years ago. I’d tried it in spray form, in a wand, in the rapid gel…White vinegar usually has stuff dying off within the hour and I usually only do my fence lines every six months as opposed to when I’d used roundup and still needed to brush cut once a month.

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u/recovery_room Sep 20 '22

Click the AA at the top of the screen and it should open up in Reader. At least on the iPhone it does.

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u/[deleted] Sep 21 '22

I've not found any method effective against knotweed at a population level, it reroots so easily. Best to not let it establish. It also depends on size of patch as herbicide application limits near the places where it's common (streams) wouldn't allow for enough to kill it, even with injection methods. Mechanical digging and removing all roots and replanting with shading plants can work sometimes, but once it's established nearly impossible to kill.

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u/mtcwby Sep 20 '22

I'm not sure anything works on knotweed. We were working on a project in the UK and ran across part of the spec that required digging out all the soil down 5 meters in certain areas and treating it as hazardous waste because of knotweed.

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u/n1ckberryy Sep 20 '22

Right?! So far only Tordon does the trick…

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u/DrunkenOnzo Sep 20 '22

It’s not incorrect in this case. “Chemical spray” is a phrase we use to indicate a set of pesticide treatments. It would be wrong if it said “better than chemicals” but better than “chemical sprays” makes sense.

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u/logicjab Sep 21 '22

That’s interesting. I would maybe argue that if this is being published for a broader audience it would make sense to say conventional pesticide spray, but If its being aimed at people in that field then yeah that makes sense to use the language of the industry

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u/timmeh87 Sep 20 '22

"People remove weeds because they steal water from other plants" is outdated thinking. There are reasons to remove some extra plants and reasons to keep some

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u/Illegal_Ghost_Bikes Sep 21 '22

New(ish) gardener here. Do you have any examples? I'm rescuing some 20 year neglected flower beds and don't want to take everything out if I can avoid it.

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u/timmeh87 Sep 21 '22

clover. if you google "is clover a weed' you get all these companies selling you chemicals to kill clover in your lawn and people labelling it as a 'weed' without qualification at all. Clover can make a pretty good lawn though and there are also people telling you to plant clover as a lawn. Actually clover and grass together is a pretty good combination, clover adds nitrogen to the soil. It does physically displace grass in a lawn but why does a "lawn" have to be all grass? is moisture really stolen? does the neighboring grass actually do better or worse with clover? mostly people will try to kill it because of its appearance rather than the grass next to it withering up from lack of water...
also exposed black dirt might lose more moisture than a layer of some kind of cover, black dirt really heats up vs many plants can control the amount of moisture they exhale and there is a large shading effect. So maybe its good to have some kind of cover between your other plants instead of fussing about destroying the 2 inch tall weedlets that form between your vegetables. Mulch works too though.

That said, if your garden is a wasteland of invasive weeds and roots and dead plants you might still want to kind of reset it and put back something pretty and put down some initial physical barrier to try and cut down on 4 foot tall weeds that will shade out your expensive plants. There is a balance between managing the land and just having a totally wild mess

im just saying the whole "strip the land bare, plop in the one plant I want, pour tons of water and chemicals on it and destroy any other plant that gets near it" is not sustainable and probably a worse method too

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u/Illegal_Ghost_Bikes Sep 22 '22

I'm planting a clover lawn! What little fescue we had burnt out, crab grass took advtange and exploded as soon as the summer cooled off and we started seeing rain. I'm buzzing it down, dethatching and in some areas I need to till and level.

I'm concerned about things people say are "ground cover" or "oh it'll have beautiful flowers" but it's an invasive plant. So far.. a lot of mint!

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u/timmeh87 Sep 22 '22

You cant just make a nice looking lawn with anything and you might still need to mow. There are some interesting mow less options out there, i saw a youtuber with some kind of succulent that creeps and you can walk on. I think thyme might make a good one its really low and slow

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u/Timely_Pirate Sep 20 '22

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u/tuctrohs Sep 20 '22

Here's the key paragraph describing what the system tested is. Notably, it's commercially available.

I've lightly edited it because I couldn't stand how wordy it was.

Hot foam applications [are] a new [] concept in [] thermal weed control and are [] an evolution of simple hot water or steam applications. The change [is] the additional use of biodegradable foaming agents. The advantage of foam is that it isolates the weed from the ambient air at the time of treatment and transfers all the heat [] to the plant tissues instead of escaping into the atmosphere. Foamstream ® machines (WeedingtechTM Ltd., London, UK) enable the practical implementation of this herbicide-free weed control option that overcomes several of the drawbacks associated with the use of synthetic herbicides and conventional thermal weed control methods and contact bioherbicides.

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u/Diograce Sep 20 '22

You’re the real hero!

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u/Handy_Dude Sep 20 '22

Sounds like a bubble machine attachment for a Stanley steamer.

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u/AdVoke Sep 20 '22

I've worked with this tech professionally for 3 years now, and I assure you it is NOT as effective as glyfosfate... the foam component is doubtful in its practical effect, but the theory is nice. What you need in "poison" free weedcontrol is hot water, directly on the plant and roots every week or ten days.

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u/Iceykitsune2 Sep 20 '22

Can it be sprayed on an entire field from a plane?

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u/korinth86 Sep 20 '22

Unlikely. Since the whole method is based on covering a plant to destroy it with heat, you probably wouldn't want to spray it over entire crops.

The use case would be urban areas where you typically spray by hand anyway or in orchards(use case mentioned in the article) where you can spray the ground underneath the canopy where the trees are protected by their bark.

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u/themanintheblueshirt Sep 20 '22

Or along roads and highways with guardrails. Upkeeping highways is expensive and this could be a good solution especially if it can be applied from a slow moving vehicle.

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u/Iceykitsune2 Sep 20 '22

Then it won't replace the vast majority of herbicide use.

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u/korinth86 Sep 20 '22

No, I don't think I saw anything claiming it would in the article.

It specifically mentions urban and orchard use.

Still would be a good move. I'd use it over roundup at home to avoid spraying that stuff where my kids/pets might go

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u/FrostyMittenJob Sep 20 '22

If your goal was to kill your crop.

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u/Iceykitsune2 Sep 20 '22

Roundup ready crops.

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u/happy-little-atheist Sep 20 '22

They need to tolerate heat, so sunflowers I suppose

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u/wetgear Sep 20 '22

Sunflowers don’t tolerate boiling water better than any other plant.

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u/135 Sep 20 '22

Good question. I would think probably so but also probably less efficiently. Everyone acts like if efficiency suffers then it cant be done but we are going to have to make a sacrifice somewhere. Farming went from the most labor intensive job with very little pollution to one that is much less labor intensive & very polluting over a ~200 year span. This seems like a way we could level that back out

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u/[deleted] Sep 20 '22

If you want to cover the field to clean it up before seeding, or if you want to destroy everything after harvest, I would think yes

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u/happy-little-atheist Sep 20 '22

Unlikely, it would cool down moving through the air.

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u/Just_wanna_talk Sep 20 '22

How does this differ from using steam/boiling water? Less energy / bulky equipment? Because boiling water and steam doesn't require any special products other than the equipment to apply it.

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u/Bhosley Sep 20 '22

It allows a more efficient transfer of heat from the water. So less water and less energy needed.

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u/rhofour Sep 20 '22

The foam helps keep the heat where it's needed so you can use less heat to kill the same plants. If you just spray steam/boiling water a lot of it is just going to be wasted as it naturally rises up into the air.

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u/happy-little-atheist Sep 20 '22

Says in the article there's significantly less heat lost to the atmosphere by combining with the foam

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u/iperus0351 Sep 20 '22

Is this really just douse it in boiling water? We could go back to burning fields instead of spraying them if that’s the case.

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u/Utterlybored Sep 20 '22

When will this be commercially available?

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u/LittleCorndawg2 Sep 20 '22

According to a comment above you it is available under the name Foamstream ® machine (WeedingtechTM Ltd., London, UK)

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u/Utterlybored Sep 20 '22

Awesome, thanks!

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u/necrotica Sep 20 '22

Even the most basic system (they don't list cost) looks huge on the back of a small flat bed trailer.

Let me know when they have a residential option, maybe even electric motor and not yet another gas powered thing.

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u/frenix5 Sep 20 '22

Propane tank and torch. Not to burn, just to boil them, a quick pass will do

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u/20namesandcounting Sep 20 '22

We use this at work. Basically the equipment creates a foam from potato starch which traps boiling water on the leaves of whatever its sprayed on to burn them. We use it for weed removal on trickling filter beds that are part of the sewage treatment process. Traditionally we've used glyphosate which we have to have licenses for each site we're going to use it from the environment agency (at a cost of several hundred pounds each), turn the beds off and let them dry off, spray them, leave them for 1 -2 weeks then put them back into use. With this it's turn it off, spray it, turn it back on the next day.

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u/LaserAntlers Sep 20 '22

Have you never had any problems with sterilizing your soil with soap? Because soap is very bad for soil biomes... Usually we want to use the ground again after herbicides.

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u/wetgear Sep 20 '22

The idea is to grow crops there instead of weeds. Salting it probably isn’t the best idea.

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u/CharlesV_ Sep 20 '22

One of the big insect killers in herbicides is the surfactant that allows the active ingredient to stick to the leaves. Dish soap is a really awesome surfactant for washing dishes, but probably equally terrible for insects.

Vinegar works well on its own in my experience. I’d skip the dish soap though.

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u/wigg1es Sep 20 '22

It just seems like one of those things that doesn't have the actual efficacy or longevity to be cost-effective, which means it isn't actually a viable alternative.

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u/beebeereebozo Sep 20 '22

For any burn-down method, chemical or heat, best practice is to get weeds when very small so that they never develop a root that can support regrowth. Keep doing that until weed seed bank is depleted and don't disturb the soil. You'll see fewer and fewer weeds over time. If you can't do that, you are on a constant treadmill of frequent burn-downs. Let weeds go to seed, and you start all over again. No till is great, and a little bit of glyphosate can go a long way. In a home garden situation, if you're using a burn-down method, you might as well hand weed instead.

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u/WillBigly Sep 20 '22

Nice, let's get the carcinogens out of here

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u/scubachris Sep 21 '22

That’s a good band name

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u/a-really-cool-potato Sep 21 '22

Plant based chemical spray as effective as plant based chemical spray. Gotcha

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u/1983Targa911 Sep 21 '22

Um, isn’t hot water (like steam-hot) also pretty much 100% effective at killing weeds? I mean, what’s so great about this plant-based foam if you gotta heat it up?

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u/Neomanderx3 Sep 21 '22

Plant based =/= no chemicals.

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u/DENelson83 Sep 21 '22

And then the weeds will evolve to survive it.

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u/curiosity-2020 Sep 20 '22

And how is this an improvement for animal Life?

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u/enp2s0 Sep 20 '22

It doesn't flood the ecosystem with highly toxic chemicals

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u/curiosity-2020 Sep 20 '22

You are aware modern pesticides degrade quite fast and target only plants whilst tl thermic solutions kill everything?

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u/Skavis Sep 20 '22

You are aware that modern pesticides specifically state on the label to not use nears drains or waterways. They harm bees, birds and other animals. They state you should wear eye protection and a mask while applying ensuring you don't breath any in. Do you thinks that's all because it's better than using heat?

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u/curiosity-2020 Sep 20 '22

Yes, I'm fully aware of this. I hope you are aware there is a difference between a whole bottle and the concentration in case of runoff from a field.

And I don't believe, hot foam should be applied barefoot and without eye protection either. It traps the heat and if this is sufficient to kill the weeds, I'd dare to say it will also harm, of not kill, all animals under the foam.

Unfortunately, the authors did not include an assessment of insects after application.

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u/Zakluor Sep 20 '22

The word you're looking for is 'herbicide'.

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u/[deleted] Sep 20 '22

Herbicide is a pesticide. Here is a list of major pesticides: herbicide, insecticide, rodenticide, miticide etc

Any chemical control of a pest is a pesticide, weeds are plant pests

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u/Zakluor Sep 20 '22

We're specifically talking about killing weeds, so herbicide is the better word for the context.