Physan and snail eradication.
 

I have been trying various methods to eradicate bush snails in my collection of about 200 orchids. I hunt for bush snails in my orchids most every evening and crush them when I find them. Some evenings now I don't find any, other evenings I may find one or several.

I have also experimented to find a snail poison that I could apply to the pots to kill snails that are hiding.

I had tried a saturated solution of caffeine (about 2% to 3%). If a snail is placed into a few drops of this solution on my potting bench it will quckly extrude its body from its shell and die. I have tried spraying pots with 3% caffeine solution to completely wet the media in hopes of killing snails but I find that this also causes damage to orchid roots. A less concentrated caffeine solution might not damage the roots but it is also much less toxic to the snails so I have abandoned trying to use caffeine to eradicate snails.

I have found that dilute solutions of Physan-20 will also kill snails. If a bush snail is placed in a few drops of 400 ppm AI (Active Ingedient) Physan-20 solution it will stop moving; if it is left there overnight it will be found to have not moved at all during the night and so it is presumably dead (I do need to verify this though) but if the snail is removed from the solution after about a minute it will eventually start moving again. So it seems that being immersed in 400 ppm AI Physan-20 solution (about 2 teaspoons of Physan-20 per gallon) for between 1 minute and 8 hours will kill bush snails. If I determine that say 15 minutes to 1/2 hour of immersion is sufficient to kill the snails then immersing pots in a 400 ppm AI solution of Physan-20 may be a viable method for exterminating bush snails.

Does anyone have experience with immersing orchid pots with orchids in Physan-20 solution (about 2 teaspoons of Physan-20 per gallon of water)? Can this be done for a 15 to 30 minute period without harming the plants and roots?

Have you tried FeO4P ? (the safer way to attract and kill mollusks)(irritating but at least not dog/cat/hedgehog killer)

Iron phosphate bait? No, I have not tried it. From the reports that I have seen I would not expect it to be effective in erradicating bush snails.

Physan-20 is not known for killings dogs, cats etc. Perhaps you were thinking of paraformaldehyde baits.

David.

Stop crushing them! As satisfying as that might be, the snails are "egg transporters", so you may actually be helping spread them.

My understanding of iron phosphate is as yours - nope.

I kept the dregs from the coffee pot, added ~10% isopropanol to keep mold at bay while in storage, and that seemed to work after several, thorough sprayings.

I have never dunked plants in Physan solutions, but have thoroughly sprayed and saturated the pots with it up to a TABLESPOON per gallon, and saw no issues. However, it may be that I don't grow plants that are sensitive to it. Personally, I'd be wary of a 30-minute soak.

If you can find a way to get hold of a metaldehyde bait - or get a pest control company to apply it for you, that's the sure way of getting rid of them.

I suspected that that might be the case so I use tweezers to remove the snails from the pot _before_ I crush them.

I can get metaldehyde baits here is California. I was looking for a less toxic alternative but if the Physan idea does not pan out then I will be back to considering metaldehyde baits. If I use metaldehyde bait then I would like to do so as judiciously as possible. Can I put just one or two pieces of bait in a pot and expect that the bush snails will quickly find it? Does anyone know of a brand of metaldehyde bait that they find especially attractive to bush snails?

I experimented to refine my estimate of how long the snail has to remain in the 400 ppm AI Physan-20 solution for mortality to occur: 15 minutes was not enough but 60 minutes was.

How about acephate; has anyone experimented with its efficacy against bush snails?

Here is the paper that got me to experiment with SA-20. See table 1 on page 4.
http://wet.asu.edu/Biological%20acco...r%20snails.pdf

A simple google search confirms that it is a molluscicide. You were correct in suggesting it - but have you tried it ?

Molluscicide - Wikipedia, the free encyclopedia

It's the common snail/slug killer in Europe (outside of organic compatible weapons like the potato or carrot slice for the valiant snail crusher, or beer)

Metaldehyde is on the way to be banned, if it's not already the case… (checking the french agricultural ministry…) it's not banned yet, but more and more difficult to find, and the information it's dangerous to pets, kids and hedgehogs has moved people to safer options, like FeO4P.

FeO4P is irritating to mammals but way more safe, it does not kill pets or hedgehogs, it degrades into nutrients for plants.

Physan is not allowed for culture here, due to the regulations on the protection of free waters. By the way, it's a strong irritant for us.

What then do you use in France to control algae in swimming pools and spas?

Hey DavidCampen,
thanks for the info on Physan-20. Has soaking the pot been working out for you? Are the plants able to do well after a 60 min soak?

I just found a slug in my new plant, and if it has worked for you, I am highly tempted to try it!!

Thanks!

Physan is toxic to mammals, as well - like us.

Strong coffee does indeed work, and can be applied without damaging roots.

Brew strong coffee. Let it cool.

Water the plants thoroughly to saturate the medium and the roots with water. This prevents root damage from coffee.

Then apply brewed coffee, cooled to room temperature.

After an hour or two, water again with plain water to rinse out the coffee.