Snail biocontrol trial results fast-track new weapon for growers
Encouraging results from southern field trials of a new biological agent to combat snails in grain crops have researchers on track for development of a commercial control.
Recent Grains Research and Development Corporation-funded field trials of the nematode-based control on South Australia’s Yorke Peninsula, where snails are a major pest, have been declared a success, enabling scientists to progress with more refined field trials to be conducted this year in SA and Victoria.
The Victorian trials will also target slugs which were a significant problem in that state’s cropping regions during the 2011 growing season.
Conducted by Charles Sturt University (CSU) with collaboration from the SA Research and Development Institute (SARDI), the field trials in September-October last year involved one combination of a native nematode and a symbiotic bacteria.
Professor Gavin Ash from the CSU’s EH Graham Centre said the biocontrol was applied in high and low rates against conical and round snails and was compared with application of metaldehyde-based baits. The trial involved 16 replicated plots each of 100 square metres.
Dr Ash said the biocontrol was just as effective as the metaldehyde bait when applied in high levels, and offered a reasonable level of control at the low rate.
While the impact was more significant on conical snails than round snails, Professor Ash said that result was applicable to both the biocontrol and the metaldehyde.
“We are not sure why that occurred in the field – unlike the laboratory – but weather conditions may have been a factor,” Dr Ash said.
“But given that these were the first large field trials that we had conducted and that they only involved just one nematode/bacteria combination – we have a total of five different isolates in production – we are very heartened that we achieved a reasonable kill overall.”
Dr Ash and his team are now preparing for a series of field trials this coming autumn which will involve a different approach.
“We will be looking to exclude the snails from the paddocks being cropped by applying a barrier of nematodes around the perimeter of paddocks using a protein-based foam formulation similar to that used in fire fighting.
“We are working with an organisation in the United States to prepare the foam formulation that will offer protection for the nematodes.”
Dr Ash said the autumn trials were likely to be even more successful than the ones conducted in spring due to the lower temperatures and moist conditions favouring snail activity.
Researchers will also be testing the optimum application rates and will consider pasture trials in addition to in-crop trials. They will continue to sample sites after all the trials to monitor nematode levels in the soils.
Dr Ash is optimistic about the biocontrol’s potential, now that the agent has been successfully tested in the field and in the laboratory.
“Nematodes have all the characteristics of a perfect biocontrol agent and they have been successfully developed for the biological control of other invertebrate pests in Australia,” Dr Ash said.
“These nematodes are fast acting organisms; once they enter the host through natural openings, they release their symbiotic bacteria that lives inside their guts, the bacteria grows in number, turning the host’s inner body into food for the nematodes. The host dies soon after.
“They are naturally occurring, soil dwelling organisms which are harmless to mammals and other beneficial animals, but most suitable to use against pests, such as snails and slugs, which live all or part of their life cycles in soil. So unlike conventional bait, nematodes don’t contaminate the food chain.”
The development of an alternative control for snails is encouraging news for grain growers in the southern region where snails again presented as a major pest issue during the 2011 cropping season.
GRDC New Farm Products and Services program manager, Paul Meibusch, says snails in particular are a significant and costly in-crop pest issue and pose a risk to grain exports.
“Snails feed on emerging crops, clog up farm machinery and contaminate harvested grain,” Mr Meibusch said.
Mr Meibusch said the last economic study commissioned by the GRDC to assess the impact of snails on farming systems showed a direct cost to farm businesses on Yorke Peninsula and in the Lower North of SA was an average $59,180 per farm or $41 per cropped hectare.
He said the development and commercialisation of a biologically-based control agent had the potential to dramatically improve current control techniques and reduce farm costs.
In the meantime, more information on snail management is available through the publication Bash’Em, Burn’Em, Bait’Em: Integrated snail management in crops and pastures, which is available from GRDC’s Ground Cover Direct. Visit www.grdc.com.au or free phone 1800 11 00 44 or email firstname.lastname@example.org.
Caption: Professor Gavin Ash is optimistic about the biocontrol’s potential.
Caption: Snails feed on emerging crops, clog up farm machinery and contaminate harvested grain.
• For more information contact Gavin Ash at Charles Sturt University on 02 6933 2765 or 0406 705169, or Paul Meibusch at the GRDC on 02 61664500
• GRDC project code: UCS00013
• This media release and other media products are available via www.grdc.com.au/media
GRDC Project Code