A combination of cultural or on-farm practices and well-timed baiting is the most effective approach to controlling snail populations. This is the finding of a GRDC-supported research initiative through the South Australian Research and Development Institute (SARDI).
“Our key finding so far has been the importance of cultural control, not only in killing snails over summer, but in improving baiting efficacy,” Mr Gontar says.
“Where no cultural controls were undertaken, we still found untouched baits several weeks after baiting, whereas after rolling or light tillage, the baits were more accessible to the snails, so they were all taken.”
The trial showed areas that were rolled or tilled and baited with metaldehyde resulted in the lowest snail numbers, whereas areas where stubble was retained resulted in the highest populations regardless of bait application (Figure 1).
Figure 1 Live snails following treatment at Coulta.
Working with Mr Gontar, SARDI entomologists Michael Nash and Helen DeGraaf have been analysing the sexual maturity of the snails collected during the trial.
“They saw that the snails were at sexual maturity from mid-March, with the first egg-laying observed in the field on 21 April,” Mr Gontar says.
“The season didn’t really break until May this year, so growers who baited at seeding or later would have been too late to kill snails before egg-laying.”
The researchers are investigating snail behaviour in more detail and aim to better understand the triggers that lead to snail feeding in summer and early autumn.
SARDI research has also studied the effectiveness of metaldehyde and ethylenediaminetetraacetate (EDTA)
baits following exposure to environmental conditions.
“Temperatures above 40 degrees, not ultraviolet light exposure as previously thought, is a cause of bait degradation,” Ms DeGraaf says.
“This gives a guide as to when it is too hot to bait in summer. If temperatures in the sun are likely to exceed 40 degrees, the baits are not going to last long before their effectiveness decreases.
“This means that growers who have stored their baits in sheds over summer may get to baiting time and find the baits are less effective than expected.”
EDTA (iron-based) baits did not show the same decrease in performance after exposure to high temperatures. However, their effectiveness was significantly reduced after rainfall.
“If growers pay attention to how they store and use their baits, whether they are using metaldehyde or EDTA products, they can help ensure their baits are doing their job,” Ms DeGraaf says.
“For instance, only picking up metaldehyde baits later in the summer, or storing them in a cooler shed, will help ensure they are in prime condition at baiting time.”
Snail control measures
- Combining cultural and chemical methods can help optimise snail control.
- Bait when snails are actively feeding and before egg-laying. This may occur after rainfall in late summer or early March. In summer, relative humidity of 90 per cent is likely to result in snail activity, whereas in cooler March temperatures, 80 per cent humidity is enough to expect snail movement.
- Keep metaldehyde baits below 40 degrees C, both during storage and when applying bait.
- Avoid applying EDTA baits when 10 millimetres or more of rain is forecast.
- Expect most baits to remain effective for about two weeks after application before they need to be replaced.
- Baits that develop mould in the paddock should still be effective.
Blake Gontar, SARDI research officer,
0430 597 811,
Helen DeGraaf, SARDI entomologist,
08 8303 9543,
Snail Management Fact Sheet
Snail Bait Application
Bash'Em Burn'Em Bait'Em: Integrated snail management in crops and pastures
Snail Identification and Control: The Back Pocket Guide
GCTV Snails playlist
End of GroundCoverTM issue 126 (southern edition)