Physan and snail eradication.

[DavidCampen]

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?