An increase in slug and snail populations has been reported by growers in central and southern NSW grain-growing regions during the past couple of years.
As a result, growers are now encouraged to monitor and manage snail and slug numbers to ensure they protect establishing crops.
The Grains Research and Development Corporation has invested in research into slug and snail ecology and control which suggests the move to minimum till in the farming systems has created a more favourable habitat for the persistence of these pests from season to season.
Retained stubble and improvements to soil structure as a result of minimum till practices has seen an increase in soil moisture-holding capacity, soil macropores, organic matter and available calcium, which has resulted in population increases and a wider geographical spread of slugs and snails.
According to this research, growers should now be considering baiting in areas where snails and slugs have become active.
South Australian Research and Development Institute entomology program leader Greg Baker said moisture was the biggest determining factor for breeding, and with snails currently becoming active after summer dormancy, now was an ideal time to start baiting.
‘‘Both snails and slugs can be controlled in no-till, full stubble systems if growers understand where and when controls are applied, and follow a few basic guidelines,’’ Mr Baker said.
‘‘Snails won’t begin mating generally until moisture levels increase, and while dews or cooler temperatures at night in autumn may begin that process, eggs won’t be laid until we receive significant rainfall.
‘‘So now it is an ideal time for baiting and by using the recommended rates of bait, growers can generally drive down numbers significantly.’’
Mr Baker said growers who have noticed a high density of snails should bait at the maximum label rate, and then monitor in the following days to determine the need for a follow-up bait treatment.
‘‘To count them, growers need to get down on hands and knees and use a quadrat (eg 30cm x 30cm), and only count the live snails, which will be juicy rather than dry if squashed,’’ he said.
‘‘It is also important to ensure the bait is being consumed by the snails, not by mice.
‘‘If baits are disappearing with no corresponding dead snails, this may indicate a mouse problem.’’
■Snail and slug baiting guidelines are available at: www.pir.sa.gov.au/——data/assets/pdf—file/0004/286735/Snail—and—slug—baiting—guidelines.pdf
■More information on snail control can be found in the GRDC Snail Management Fact Sheet at: www.grdc.com.au/GRDC-FS-SnailManagement