Snail plague in S.A.
 

I find this story extraordinary. I had no idea snails could get to this sort of problem.

http://www.abc.net.au/news/2012-05-0...insula/3991336

Snails are such good food for a lot of predators, it seems to be an ecosystem way out of balance.

instead of fighting against them , maybe they should farm them, there must be a market for local escargot surely ??
yum yum.

monoculture? nowhere for the blue-tongues to hide and whatever else eats snails. Maybe those snails don't taste very nice to potential predators?

The snails were introduced accidentally, probably in ship ballast, some time last century.

They are from the Mediterranean region and there are the four breeds; two round and two conical-shaped snails.
*Well there's you're Problem*

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Oh dear. I see the ABC has cleaned up the spelling, but the punctuation is iffy.

They are from the Mediterranean region and there are the four breeds; two round and two conical-shaped snails.

The problem is that funding for biosecurity is so bloody woeful. It's hard to keep people on the ground to deal with invasive species http://www.discussworldissues.com/fo...lies/frown.png

They've been working on this problem for decades. Here's a PDF of a short book (44 pages) that has lots of info about the snails and techniques for their control.

The introduced Mediterranean snails are the reason why the ‘ecosystem is way out of balance.’ They are weed-like in the rapid rate they can reproduce, plus they lay their eggs in the soil and the young do not all emerge together so they can be knocked off in one go. Some seem to take several years to emerge, thus making control over large areas almost impossible.

Like most snails they enjoy eating young herbaceous vegetation during the cool moist periods of winter/spring, but then climb off the ground to escape the very hot summer temperatures at ground level, hence the great clusters of snails on those fence posts. These clusters cause problems as they can interfere with feeding stock and will clog up farm machinery. In some unmanaged paddocks, the snails (thick on remnant vegetation and weeds) can be seen as far as the eye can see. No wonder some people refer to this country as ‘heart-break country.’

Near where I live, there are calcareous tertiary dunes where these Mediterranean snails occur, these dunes end abruptly and acid sandy soils (heathland) begin. Interestingly, the snails are common right up to the acid sand boundary then stop and despite spending a fair amount of time looking, I have not found them over this line.

I would think one of the reasons why these snails are not interested in exploring the acid soils is because there is no calcium there to make their shells, whereas in the alkaline soils, limestone is part of the environment.

If it were not an ecosystem problem the snails would take over the whole of southern Australia. The farmer said "All my life there's been snails on the property, but it wasn't until 1998 when we had a significant problem,"
All plants need calcium, it's not just found in calcareous soils.

That seems a reasonable hypothesis LooktoSee.

Do you their natural predators within in their native range?

Thanks Helix.

All my questions dealt with.

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"Why snail numbers have rapidly increased in southern Australia is not
well understood. The adoption of conservation farming where there is
stubble retention, less burning and less tillage are factors which may
have resulted in increased snail populations, especially in the calcareous
and highly alkaline soils. Consecutive seasons of above average winter
and spring rainfall may also have contributed"

I have had infestations of the small conical snail at my place. The snails have been widely distributed across southern Australia for many years.

.
Some seem to take several years to emerge,
---------------------------------------------

Are they using the (slighty) prime number birth rate to aviod perennial predators?

Viable eggs hatch in a few weeks.

Well something is going on then, as I had ducks that loved eating the snails, these were fenced in, as the foxes loved eating the ducks. Anyway, they were very effective at eating all snails from their enclosed area, but other small snails continued to emerge for several years despite their efforts. Some snails moved in from outside, but these did not last long.

By the way, I no longer live in these calcareous sands and moved to the snail free, acid soil heathland where bio-diversity is much higher.

As for predators, there may have been some, but the numbers of snails are so high that they had no affect. To control them would need vast numbers of something like microbes or fungi.

>>All plants need calcium, it's not just found in calcareous soils.
Acidic, sandy, or coarse soils often contain less calcium.

I will kit myself with a pH test kit and go snail counting and photographing.. There are millions in my yard and billions outside the gate. I don't have the common garden snails or should I say.. their numbers have decreased from around 500 per sq m to about 5 in 1600 sq m., in the last 20 years. Over the same time they have been completely replaced by these http://farm5.staticflickr.com/4046/4...8d9b38f049.jpg http://farm6.staticflickr.com/5218/5...7a7ef1f897.jpg

Metaldahyde is no solution as it kills the other possible parasitic and predatory balances. Methiocarb is worse. Iron chelates bait works better if it is very liberally broadcast but this can only improve the calcium problem.

By the way.. Before I moved here, I lived on rice growing clays.. I didn't have the white snails.. only the common garden snails. When I moved here.. I moved onto calcrete at the surface and as far as I can dig into the pinkish clay that turns white as soon as you air it.. The pH between the two sites as you may imagine is vastly different. I'm sure this is an experiment we can all try, if we have the various species of snails and the various clays and sands.

http://img.photobucket.com/albums/v6...d/DSC_0443.jpg


Crushed snail is a recipe for cement basically. There is an industry for an entrepeneur.

"By the way, I no longer live in these calcareous sands and moved to the snail free, acid soil heathland where bio-diversity is much higher."

These same snails are very prevalent on Etre peninsula too, which has some of SA's highest biodiversity.
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I was horrified at the burning of the roadside veg going in to one of my favourite conservation paks, until I realised it was a snail reduction measure.

devil and deep blue sea stuff.

>>These same snails are very prevalent on Etre peninsula too, which has some of SA's highest biodiversity.

I wonder if this is caused by conservation farming. Helix's article suggested it as a possible cause. Conservation farming is a method based entirely on pesticides, some of them fairly potent, long lasting sprays. It is good for increasing organic matter content, but all those chemicals have to be a concern. I'm not against chemicals per se, but they need to be used carefully. I read about glyphosate resistance in the US last week, NYTimes, They are having trouble with their roundup ready seeds, now they are creating strains resistant to 2,4,D. That's a different issue, but related. If the problem is mainly in farmland, it's probably due to farming practices.