Paddock Practices: Be aware of snails at harvest

Key points

• Snails pose a significant biosecurity risk. All farm vehicles and machinery should be checked before entering properties.
• Harvesting during the day can result in fewer snails being found in harvested grain.
• Swathed or windrowed crops should be harvested as soon as practicable to minimise snail contamination.
• Grain cleaning should only be used as a last resort and should not be relied upon for removing snails from grain.
• Year-round integrated management is the key to successful snail control.

With harvest fast approaching, growers are reminded of the importance of minimising the spread of snails by prioritising the order of paddocks to be harvested.

Snails pose a significant biosecurity threat as they are easily transported between paddocks, farms and regions. Therefore, it is important to inspect and clean equipment, machinery, vehicles and fodder prior to them entering a grower’s property.

Research conducted by the Department of Primary Industries and Regional Development (DPIRD) in Western Australia has found that harvesting during the day between 11am and 6pm resulted in fewer snails being found in harvested grain.

Further to this, DPIRD research officer Svetlana Micic says one of the key recommendations is to harvest paddocks with high snail numbers last, if possible.

“Cleaning machinery after harvesting snail-infested paddocks has been difficult,” she says.

“Our research has shown that snails still get left behind despite cleaning machinery with pressure washers and compressed air.”

Crops that have been swathed or windrowed should be prioritised and harvested as soon as practicable, according to Ms Micic.

“The longer a swath is on the ground, the more vagrant insects tend to be found and incidentally harvested,” she says.

“Swath height should also be considered as swaths that are close to or on the ground tend to have more vagrant insects in the grain.”

Ms Micic says it can be difficult to remove snails once they are present in grain, especially if the snails are the same size as the grain.

Grain cleaning should only be used as a last resort and should not be relied upon for removing snails from grain.

According to the GRDC’s Snail Management fact sheet, using a stripper front at harvest can be an effective way of reducing snail contamination in medium to heavy crops.

By vibrating snails off standing cereals and taking in less material, stripper fronts reduced snail contamination in grain by 50 per cent compared to a standard open front.

At the same time harvest ground speed and harvest capacity were increased by up to 100 per cent in suitable conditions. A cheaper but less effective alternative is to raise the cutting height and add a dislodger bar.

Ongoing management

Primary Industries and Regions SA’s (PIRSA) research and development arm, the South Australian Research and Development Institute (SARDI), has led much of the research into snails in previous years.

SARDI entomology science program leader Greg Baker says the key to successful snail control is year-round integrated management.

This includes:

• Use an integrated approach with the available tools year-round every year to limit snail build-up.
• Remove summer refuges such as summer weeds.
• Roll or cable in summer when temperatures are above 35 degrees Celsius.
• Bait before egg laying in autumn. Research has shown that egg laying can occur before sowing so baiting at sowing or after is often too late.
  • Baiting in winter is less effective because baits compete with green plant material, which is more attractive to snails.
• Harvester modifications can decrease snail contamination in grain.
• Use grain cleaning as the last resort.

GRDC research

A GRDC investment led by SARDI in collaboration with the University of South Australia, DPIRD in Western Australia and a number of farming systems groups, builds on previous research and is investigating the environmental conditions that lead to feeding and reproduction.

The work aims to assist growers to optimise the timing of their baiting programs.

Field sites have been established across Western Australia, South Australia and Victoria to monitor the activity and biology of key snail and slug species using fixed cameras and field sampling, along with associated climate and micro-climate variables.

The research is generating insights into the reproductive patterns of snails and slugs in southern and Western Australia.

More information

Svetlana Micic
08 9892 8591
svetlana.micic@dpird.wa.gov.au

Greg Baker
08 8429 0933
greg.baker@sa.gov.au