A comprehensive series of management guidelines for the control of snails has been developed through some innovative research and help from farmers.
Scientist Megan Leyson, of the South Australian Research and Development Institute (SARDI), has focused on four snail species: common white snails, white Italian snails, conical snails and small conical snails. They are all exotic species from the Mediterranean region, most of them having been introduced to Australia in the 1920s on imported farm machinery. These hermaphroditic creatures can lay up to 400 eggs a year.
While these snails can eat a good crop and ruin it, the main problem with them is contamination of harvested grain. The smaller snail species have shells that are equal in size to grains of wheat or barley or canola and they can be difficult to remove.
Ms Leyson says the project began by contacting farmers across South Australia and testing in the laboratory and in trials their methods for managing snails.
One of the farmer-driven solutions is particularly simple and effective: snails like stubble because it gives them something to climb to get away from the soil as it starts to heat up in the warmer months - a 36°C day results in a 55°C ground temperature, which is enough to kill a snail. The answer is to knock them off the stubble onto the ground to literally stew in their own juices.
Farmers in the upper south-east of SA came up with the idea of stringing a steel cable between two tractors and dragging it across a paddock. Two runs across the paddock in the morning and the afternoon is usually all that is needed.
Other stubble management solutions for snails include slashing and using stone rollers to crush them. The project has also resulted in a shift in baiting strategy. Previously farmers in southern Australia put out bait in September.Ms Leyson says it is now recommended that baiting occur at the break of the season in autumn. When the rain comes, the snails mate. Baiting at the break hits them before the eggs are laid.
On the Yorke Peninsula, biological control has been shown to be effective.
Ms Leyson says an earlier project looked for a natural predator of snails in the Mediterranean area and found a parasitic fly (Sarcophoga penicillata) that targets the conical snail throughout its life cycle. It places a single larva in the snail shell, which feeds on the snail and kills it. It then pupates in the shell and emerges a couple of weeks later as an adult fly.
These flies were first released in 2000 as part of the current project and are slowly establishing themselves on the peninsula.
These and other management guidelines are outlined in a new 40-page booklet, Bash "Em", Burn "Em, Bait "Em, available from Ground Cover Direct on freecall 1800 11 00 44, at $20 per copy plus postage and handling.
GRDC Research Code DAS300
For more information: Megan Leyson, 08 8303 9670