Friday, October 18, 2013
Reducing the risk of snail contamination this harvest
Grain growers are advised to assess snail infestation levels in crops and determine the need
for strategies to minimise the risk of contamination this harvest.
The South Australian Research and Development Institute (SARDI) Entomology Unit warns
that snails present above cutting height in the canopy or in windrows can enter the header
during harvest, potentially leading to clogging of machinery and grain quality downgrades.
SARDI entomologist Kym Perry, whose work is supported through the Grains Research and
Development Corporation’s (GRDC) investment in the National Invertebrate Pest Initiative
(NIPI), says while it is now too late to bait, employing a combination of strategies at harvest
can considerably reduce snail contamination.
“At this time of year, the aim is to minimise the intake of snails into the header, maximise the
separation of snails and grain within the header, and where necessary, clean harvested
grain to minimise the number of snails eventually entering the grain sample,” Mr Perry said.
Mr Perry said there was generally a trade-off between snail removal from grain and grain
losses.
“Generally, reducing snail intake is more easily achieved earlier in the harvest season when
fewer snails are up in the crop canopy, moisture events may still trigger snail movement
back down plants, and snails are more easily dislodged from plants with lower grain losses.”
Some suggested techniques to minimise contamination include:
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
Harvesting snail-infested crops first where possible before all snails have moved into
the canopy. Harvesting after a light shower that has caused snails to move out of the
plant canopy can also reduce snail intake without excessive grain moisture
absorption.

Windrowing cereal crops can dislodge some round snails, however, windrows of
crops that are cut green and left to dry (eg canola, pulses) can be invaded by snails.

Dislodger bars attached to the header knock a proportion of round snails from
standing crops. They are often most effective in early harvested or windrowed crops.
The design should be adjusted for different crop types and conditions to maximise
snail removal while minimising grain shattering. Travelling at right angles to the
direction of crop lean where possible can reduce grain losses.

Stripper fronts can significantly reduce snail intake in cereal crops relative to
standard open front machines. They also allow faster harvest speeds and will smash
some snails as they enter the header. Raising the cutting height is a cheaper but less
effective option. Both approaches leave more standing straw but this may be
removed with a second pass.

Sieves and mesh screens should be set up correctly to maximise snail and grain
separation within the header. Sheet metal (punch-hole and expanded mesh) sieves
are usually more effective than louvre sieves in removing snails but have a lower
cleaning throughput, therefore harvest speed may need to be reduced to avoid
overloading and grain losses.
Friday, October 18, 2013

Post-harvest grain cleaning is the last opportunity for snail removal. A combination of
systems is usually required to meet receival standards without excessive grain
losses. Post-harvest rolling and crushing of snails is effective for all hard grains
(except canola) at the optimal moisture content. An inclined belt separator is needed
to remove small conical snails from canola.
The GRDC has published a Snail Management Fact Sheet which can be viewed and
downloaded via www.grdc.com.au/GRDC-FS-SnailManagement. It provides information on
minimising contamination at harvest as part of a year-round approach to controlling snails.
More information on harvest techniques and integrated snail management is contained in the
GRDC publication Bash 'em, Burn 'em, Bait 'em which is available for viewing and download
via www.grdc.com.au/GRDC-Snails-BashBurnBait.
Further information on integrated pest management is available from the GRDC via
www.grdc.com.au/pestlinks.
As a result of the increased prevalence of snails and slugs in the southern cropping region in
recent years, the GRDC is further investing in a number of research and development
programs which are mapping different species and looking at a range of control measures.
ENDS
For Interviews
Contact
Kym Perry, SARDI Entomology
Phone (08) 8303 9370
Sharon Watt, Porter Novelli
Phone 0409 675100
Greg Baker, SARDI Entomology
Phone (08) 8303 9544
Caption: Snails present above cutting height in the crop canopy or in windrows can potentially lead to
clogging of machinery and quality downgrades.
GRDC Project Code: CSE00046
Media releases and other media products can be found at www.grdc.com.au/media-news
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