Experimenting with CO2 as a pest control strategy
 

I’ve read about CO2 being used to kill pests in terrariums, but haven’t come across much info on using this technique on individual plants, or which insects it works on, other than reading that spidermites are unkillable this way.

I’ve been dealing with mealybugs on my orchids since 2008. Most of the time they are under control, but during the nearly yearlong period of neglect my collection got, I’ll let you imagine the situation with them... I’ve thrown out many of the plants that are in bad shape, but some are favorites that I’d like to save. Pesticides never got them all in the past, so I want to try other methods to deal with these insects once and for all. CO2 gassing being my current experiment.

I brought one infested Phal to work yesterday, since we have CO2 cylinders in the labs. I placed the plant in a bag, removing as much air as possible, then filled it with CO2 and tied it shut. I then put it in my greenhouse compartment (where I grow plants for my research) hoping that the warm temperature in there (26C) would increase the insects metabolic rate (and so the amount of CO2 they breath in). I left it like that for 2 hours, and it seems that the majority of the mealies have died! So today I’ll be repeating the treatment (I’ll do 4 hours this time), and I’ve brought a few more infested orchids...

I plan to do repeat the treatment every 3-4 days for 2 weeks (to be sure that I got them all), and leave the plants in the warm and humid greenhouse to recover, before taking them home again, and then leave them in quarantine for another 3-4 weeks. I’m hoping that the CO2 will lead to a nice growth spurt as well, the plants need it.

I’ll post my progess in this thread, in case some of you are interested in the final outcome!

I would like to hear about how the plants do after this treatment. Mealies I find easy to kill with insecticides but I would like to get rid of bush snails:
http://www2.ctahr.hawaii.edu/oc/freepubs/pdf/mp-1.pdf

They are not harmed by any insecticides that I can obtain; only the very toxic cholinesterase inhibitors that are highly restricted are reported to work. There are some molluscides available but they are not registered for general use.

I tried a concentrated solution of caffeine and also a solution of Physan at 400 ppm AI (Active Ingredient) and these will kill a lot of snails but also seem to cause damage to orchid root tips.

A pure CO2 atmosphere should kill snails. My only question is will it also harm the orchids, particularly the root tips.

For the CO2 to work it will have to penetrate into the media, displacing most of the air there. Just leaving the pot sitting for an hour or two in a CO2 atmosphere might leave significant pockets of air in the media which would allow some snails and mealies to survive but if this is problem I can think of several work arounds.

I had thought about how the CO2 would penetrate into the medium, but most often the mealies don't go down so much into the bark. I'll see how it goes, and next time I may stick the end of the CO2 hose into the bark to flush out as much air as possible. From what I've read in various places, orchids tend to do ok after CO2 gassing, often responding with a flush of new growth. I'll be taking some progress photos of the test orchids (2 Phals, 2 Dens) and will share them here.

Hi, Camille!
Good to see you on here again. :)

Do you know why spidermites won't be affected by carbon dioxide treatment??
Are they able to shut their system down temporarily or something??

It is nice that you have the facility to treat your favorite plants.
I hope you get rid of (or at least put big control over) those nasty mealies off your plants.

Nice to see that you're still around too! :)

I have no idea about the spider mites. This is just info I've come across on cannabis forums (good place to search for chemical free insect control). Maybe these people didn't have a high enough concentration of CO2, or not long enough, or their container/method wasn't airtight. Who knows?

I see.
Mite are my biggest concern. not the common redspidermites which I can at least see with my naked eyes.

I don't think I have mites but then the microscopic sized ones I heard about, sometimes I wonder if I have them everytime I see the tiny indented pockets on my paphiopedilum leaves.

Oh, well...

I had brown scale for over a year and the only thing that killed them little sob's was a good scrub and soaking them bare root over night. I know it's not ideal but no bugs and no chemicals works for me. GL

Interesting thread, I look forward to reading the results! And searching cannabis forums for chemical free insect control is genius!

Well, I have to admit I am very quick to turn to chemical megadeath in a heartbeat. I sow slug pellets by the kilo (it's a fair sized garden) otherwise we would have nothing left when the snails were on the march. I use pellets round the orcids, or I wouldn't have any.

As regards the cannabis forums, there are some pesticide residues that linger, and can't be used on leaf veg but can be used on fruit. As I'm not eating the orchids, I don't worry about it. I use confidor a lot as a good systemic pesticide.

I couldn't grow oranges here without resorting to pesticides.

I do use insecticides, but despite rotating among chemical classes, after 6 years of battling the mealies it seems like they're starting to develop resistance. And because of stricter national/EU laws, a lot of insecticides have been pulled from the market, mainly the neocotinids, which are the ones I had the most success with.

I did do a first treatment with Confidor a few weeks ago, and there seems to be quite a few mealies left. Which promted me to look for alternative measures to deal with the survivors...

One Den I treated yesterday also had scale, and those also seem to have died with the carbon dioxide treatment, judging by how easily they were to scape off with my fingernail this morning.

The orchids are now in recovery mode, and I'll keep them at the 'hospital' (greenhouse) for a few weeks, and gas them again next week. It's 75-80F in there, 70-90% humidity, good air movement and bright. So I'm hoping that these ideal conditions will negate whatever bad effects the CO2 may have had on the plants.

Very nice. I'm happy it worked for you.
I've used carbon successfully on spider mites.
Just saved an angel trumpet that way.
I've also used it on scale, mealies, aphids, and random other pests.
I have to use dry ice though lol.

Gods yes. Persistant reliance on one pesticide will give you resistance faster than you think.

I like to alternate Confidor with CHAS 48 aka Dursban. Be careful with this, and never overdose as some palnts really don't like it. I'd try it on one orchid to start with, as some plants can have a bad reaction.

You could also use helium, if you can't get CO2

I'd have no idea where to get dry ice here. My initial idea was to make, based on something I found on a terrarium forum, a CO2 generator, by mixing vinegar and baking soda.

Did you do a one off treatment, or repeat it several times?

Here they sell it in grocery stores. Normally up front.

It depends. One normally does the trick. But I usually do two to be safe.
The spider mites took 6 treatments! I've been battling those guys for two years on that stupid tree.

In grocery stores????? Wow. Here I order it from lab supply companies to use to send frozen leaf samples across Europe. But beats me why someone would need dry ice for everyday use, considering that it is something to use with caution...

I can't find any grocery or other retail store in Illinois that sells dry ice to the public, so its not available everywhere.
Keep up with your experiments. I have battled to find something to use on dens so your success is interesting, just have to find dry ice !

These are important experiments that you are doing and I am hoping for a very positive outcome; I really want to try this to get rid of bush snails. I wish I could get Dursban as it will kill bush snails but in the US one needs a pest control applicator license to buy it and it is highly toxic to mammals as well as insects.

In the US dry ice is available from ice houses but here in Southern California, in the past several years (maybe a decade, time flies), dry ice has been sold widely sold in grocery stores; a single company started putting dry ice chests in grocery stores. There is a sign on the chests that you have to be over 18 to purchase the dry ice. Also, the employees don't know how to handle it, the one time I purchased some I brought leather gloves with me but the clerk reached into the chest to grab a brick of dry ice with her bare hands and I had to stop her. It is useful for keeping things frozen when you don't have electricity.

In Southern California and probably much of the rest of the US, carbon dioxide cylinders and regulators are widely available for rent at the many hydroponics shops that have sprung up to service the marijuana growers. I have a cylinder, that I take when I drive my 4WD vehicle off road, that I use to inflate tires; I purchased my cylinder and regulator from a company that sells equipment for off road driving.

David, I just read another thread today, about killing snails in terrariums. CO2 doesn't work on them apparently...

http://www.orchidboard.com/community...cool-tank.html

As I say, you can use helium. It's inert and they sell it to fill party balloons. I don't think it would harm plants, but as always, i'd try in on my least valuable first.

That would suffocate the bugs.

It's important to consider the buoyancy of the gas you are using, too.

Carbon dioxide is heavier than air, so it will sink when pumped into a chamber with plants, slowly displacing the air from the bottom to the top.

Helium, however, rises in air, so it would be a bit more difficult to displace the air in a closed chamber.

Another heavy gas that would displace air and possibly suffocate pests would be nitrous oxide. Not sure how the plant would react though.

I think that some people use dry ice because they don't have CO2 tank and regulator (but you do).

For mealy, imidacloprid-based one (e.g. Confidor) always worked for me. Even though it is systemic, I do need to apply it a couple times. Insect-hormone based insecticide (e.g. Enstar II) seems to be pretty promising and not so scary for human. It is probably difficult to develop resistance for this (it is important to completely eradicate).

For plants I use for research, I have suffocated bugs (aphids) by submersing the plant under water for overnight or longer. Plants don't seem to mind suffocation too much. Note that respiration of plant cells increase significantly with the temperature.

I haven't had bush snail issues, but it seems like a real 'pest'.

Good point about the buoyancy. An individual plant can be put under a hood, so that the air is displaced out by the helium downwards.

---------- Post added at 02:13 PM ---------- Previous post was at 02:11 PM ----------

Drowning them? Interesting! Would it be an idea to add a tiny drop (REALLY TINY) of washing up liquid to the water? That would allow the water to penetrate the spiracles of the bugs and drown them quicker?

Oh you know. Witches cauldrons need to bubble and sometimes our morning coffee needs a special kick. Lol.

I'm not entirely sure why it's sold in grocery stores here. We use it alot to show cool science tricks to kids. And i use it alot in my garden.

How did you do that with dry ice??
Can you explain in more detail?
Apparently plants were not harmed by the cold.
I had no idea dry ice was sold at grocery stores. don't think I've seen it here. I'll have to look.

I double bag the plant in some garbage bags.
Then I set a dish of hot water in a grocery bag which I cut a few small holes into. That gets placed in the garbage bag next to the plant.
I make sure the container of water is not touching the plant as the container will get cold.

Dry ice is sold by the pound at my store. $3 a pound specifically. So I use about a pound per treatment.

I then drop the dry ice into the water and quickly tie the grocery bag loosely.
The.... is it vapour? The vapour isn't really that cold, and the hot water helps keep it warmer. The grocery bag is so no cold water will splash on the plant. .
After tying the grocery bag I thoroughly knot the two grocery bags and watch it inflate.
I tend to do it before bed and let it sit over night.

One other way I do it is to stick tubing in in the cap of a large bottle. Put the plants in a closed container, and fill the bottle with dry ice and hot water.
The bottle method tends to need refilling a few times.

I'd rather use a tank and regulator if I'm honest.

Camille, can you give us an update on your experiment?

Well so far it seem that the mealies are just about gone. I did 2 treatments a few days apart, and in a few days will do it again to catch any survivors. The Phals took it quite well and are putting out new roots now. The 2 Dens are looking fine, though the new growth of my Den tetragonum didn't like the CO2 and died off. Luckily I see a new one starting already. That plant looks pest free, so I wont treat it again so that I can preserve that new growth.

How long do you keep the plants in the CO2 chamber?

The first time I left them in the bag only a couple hours, and the second time was about 8 hours because I was busy and forgot about them all day... It's not pure CO2 though. I removed as much air as possible from the bag before filling with CO2, but I didn't dare leave the CO2 on on to flush out the remaining air. For some twisted reason, the CO2 tap is located in a closet sized room that has limited ventilation, rather than being in one of the labs which are extremely well ventilated. So I didn't feel like killing myself along the bugs...

Do you have argon on tap? Many chemistry labs do.

Since I am interested in exterminating bush snails, I googled "snail asphyxiation". Here is the first result that I looked at:
Asphyxiation / Snail Problems

No, no argon. I work in Entomology so we're all playing with plants and insects all day. Our labs are just for setting up bioassays with them or doing microbiology type work (gene expression studies mostly).

I hope you'll manage to find a solution to deal with those snails!!

Argon is also used in welding (MIG and TIG) so it is commonly available. I had a tank many decades ago but gave it away a couple of moves ago. Perhaps some day I will get another tank and try using it for asphyxiating snails. It might be that argon would do less damage to plants that CO2.

have you any ideas on eradicating bulb mites ? I wonder what they do in Europe for this feisty pest.....

David, why argon would do less damaging to plants than CO2? Your goad is to achieve low O2 level for snails and enough O2 for plants, right? Then with CO2, plants can support their respiration needs from photosynthesis at least for the leaves. So it may be better to do it during the day. With CAM, they shouldn't be doing lots of gas exchange during the day, so O2 may not be released to help snails.

My thought is that a pure CO2 atmosphere damages plants due to its reactivity/acidity and that an inert gas such as argon may still kill snails by asphyxiation without causing damage to the plant.

Hmmm, I was wrong; extremely high CO2 level is not good for plants.

This says that plants didn't have much stress up to 10% CO2:
Response of aphids and greenhouse plants to insecticidal concentrations of carbon dioxide - Journal of Plant Diseases and Protection

But this says you need quite a high CO2 level to kill even insects:
http://www.nzpps.org/journal/55/nzpp_553030.pdf
CO2 Meter - Can CO2 Kill Insects and Garden Pests?