Experimenting with CO2 as a pest control strategy - Orchid Board

camille1585 · #1 10-01-2014, 04:03 AM

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!

DavidCampen · #2 10-01-2014, 02:35 PM

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.

camille1585 · #3 10-01-2014, 03:44 PM

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.

NYCorchidman · #4 10-01-2014, 03:50 PM

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.

camille1585 · #5 10-02-2014, 03:48 AM

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?

NYCorchidman · #6 10-02-2014, 10:20 AM

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...

Phal grower · #7 10-02-2014, 11:18 PM

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

nikkik · #8 10-02-2014, 11:29 PM

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

bil · #9 10-03-2014, 04:51 AM

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.

camille1585 · #10 10-03-2014, 05:11 AM

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.