Ammonia as snail treatment?

[e-spice]

I have a isolated group of plants that has some small snails in the medium. They mostly grown semi-hydroponically, using lightweight clay aggregate (LECA) as medium. The snails are Zonitoides arboreus, commonly referred to as "bush snails" or "orchid snails." I had an some of these snails in the past and used a 1% caffeine spray which really did a good job eliminating the snails but almost eliminated the orchids too . It really stunted root and plant growth about a year and killed a few plants. I've heard about hosta growers using an ammonia solution to get rid of slugs and snails.

Doing a few experiments, a 10% ammonia solution kills the small snails on contact. I wonder what effect it would have if I saturated the top medium of the affected orchids with 10% ammonia and then rinsed with water in 30 minutes or so? Has anyone tried something like this before or care to share your thoughts on this approach?

 

[abax]

That approach scares the hell outta me. Orthene 97% is
a good first knock down for bush snails. Sometimes
Diatomaceous Earth works fairly well. Something with
metaldehyde (sp?) works better than anything if you can
find it.

 

[NYEric]

Cinnamon oil works but can damage some plants.

 

[littlefrog]

How did you prepare your caffeine spray?

I didn't spend a whole lot of time on it, but I didn't find any good literature that would support a mechanism for caffeine affecting roots (or plants in general, at least orchids). At least assuming it works similarly to how it works in animals.
But doesn't mean it isn't possible. Would be more likely that if you saw effects it was due to something that came along with your caffeine preparation.

I have not found any good controls for slugs/snails, at least in my conditions. Metaldehyde is both dangerous and difficult to purchase (for good reason). Unfortunately it doesn't seem to work very well... Replacement slug/snail baits (with iron phosphate) don't seem to do anything for me. Had been considering caffeine, actually.

 

[naoki]

Rob, there are several phytotoxicity of caffeine reported.

Batish et al (2008, Acta Physiologiae Plantarum, 30: 401-405) showed it reduces the root formation of cutting in mung beans, so it has the opposite effect of auxins.

Also here are the couple other effects summarized in Batish et al. (2008).

During seed germination, the stored energy in seeds (starch) get converted to sugar. Caffeine interferes with the enzyme to convert, so seeds can't germinate, in Amaranthus spinosus. Rizvi et al (1987, Plant Soil 98: 81-91).

Caffeine inhibits growth of rice and maize seedlings (Smyth 1992, Journal of Plant Growth Regulation 11:125-128; Anaya et al 2002 in a book "Allelopathy from molecules to ecosystems" p.71-92). Roots growths are more affected.

Caffeine inhibits mitosis in the root tips of coffee plant (Friedman & Walker 1983, Journal of Chemical Ecology 9:1099-1106)

So caffeine affects root growth. We do not know the exact mechanism yet.

Similar to e-spice, I killed quite a few orchids by following Hollingsworth et al. (2003, Annals of Applied Biology 142:91-97), who claimed that caffeine is effective in killing bush snails and that there were no phytotoxicity. Their paper showed that at 1 or 2% concentration of caffeine was really effective. I used these concentration. I got purified caffeine powder from ebay, and put 10g (or 20g) per 1 l of water to make 1% (or 2%). This is a lot of caffeine. I applied twice by drenching (1 week between the applications). I don't have the control, but the effect was obvious. The growing tips of Phalaenopsis roots disappeared quickly (within a week). Then the growths were stopped for all orchids for a couple months. About 10% of them (around 40-50 plants) didn't make it. There were differences in the susceptibility. I think Phalaenopsis were the ones which got killed at a high rate. Cattleya could tolerate.

So I wouldn't recommend trying caffeine.

Metaldehyde is relaively mild in terms of toxicity, and it quickly biodegrade. According to wikipedia (link), it breaks down to acetaldehyde, so the toxicity is similar to it. acetaldehyde is a metabolite of alcohol, so you have it after you drink wine. But the bait contains wheat, and some pets could be attracted to wheat.

Carbamate, e.g. Methiocarb (Mesurol) and Carbaryl (Sevin), seems to be a bit more scarely since it is neurotoxin.

Any chemicals can be toxic to human, and different people have different levels of comfort. I wish we could have a safer control against bush snail!

 

[e-spice]

littlefrog - What naoki said

naoki - Very informative post! I also used purified caffeine power and noticed the exact same thing you did about the phalaenopsis. They're the majority of what I lost. Most orchids from the other genera just refused to grow leaves or roots for months. You apparently know a lot about chemistry. Any guesses as to what a 10% ammonia would do to orchids?

 

[Ray]

When the caffeine thing hit the horti-news, I started collecting the dregs of my morning coffee. I added about 10% isopropyl rubbing alcohol to keep mold at bay (it does not work well). I poured it generously over affected plants, and the snails died or left.

What more can I say...

 

[naoki]

e-spice, ammonium as a molluscicide is something I haven't heard of, so I'm starting to read more about it in scientific literature. I briefly replied to your post on OrchidsForum, but I don't know if it is toxic to orchids. When we talk about nitrogen source (NO3 vs ammonium), many plants show ammonium toxicicity, but some plants are more tolerant. However 10% ammonium is way beyond what we use as the fertilizer. I'll need to read a bit more about the effect as a molluscicide and phytotoxicity.

Probably, spent coffee has very low caffeine concentration (0.07% or so for the brewed coffee). Hollingsworth's report showed that even with 1% caffeine drench, mortality rate was around 60%, it was around 95% with 2% caffeine. So it is unlikely that caffeine was the cause. Coffee could contain other compounds. There are some molluscicide derived from plants. e.g. Yucca, phytolacca dodecandra, or Cardenolide extracted from Adenium arabicum and Calotropis procera. So it is possible that other components of coffee might have worked for you. There is a good review of plant-derived molluscicides in
Kloos, H. and McCullough, F.S., 1982. Plant molluscicides. Planta medica, 46(12), pp.195-209. (link to pubmed, but I'm not sure the link to full text there works)

 

[e-spice]

When the caffeine thing hit the horti-news, I started collecting the dregs of my morning coffee. I added about 10% isopropyl rubbing alcohol to keep mold at bay (it does not work well). I poured it generously over affected plants, and the snails died or left.

What more can I say...

Ray you must either not have many orchids or must be one heck of a coffee drinker or be able to treat your entire collection