Spreader trial slugs snails
GroundCover™ Issue: 108 | Author: Rebecca Jennings
Snail and slug infestations are a costly problem for Australia’s grain growers, carrying a conservative annual price-tag of $40 million in grain value loss, harvester damage and grain cleaning – not to mention threats to market access.
Growers in South Australia’s Yorke Peninsula know all too well the challenge of managing mollusc pests. During peak breeding times, as many as 2500 snails per square metre have been recorded in the region.
Local growers rose to the challenge last August, when the Yorke Peninsula Alkaline Soils Group (YPASG) trialled the most effective ways to bait snails as part of a GRDC Regional Fast Track Project.
Project supervisor and third-generation grain grower Ashley Wakefield has seen snail populations boom in recent seasons on his central Yorke Peninsula property ‘Tingara’.
“The past couple years have been good growing conditions, but unfortunately they have been good for snails too,” Mr Wakefield says. “There have been good summer rains and cooler temperatures, so control strategies such as cabling and rolling have not been as effective.”
The ‘bash ’em, burn ’em, bait ’em’ integrated approach to snail management incorporates control options such as cabling, slashing or rolling to knock snails off stubble stalks onto the hot ground (most effective on days over 35ºC), strategically burning stubble, and baiting paddocks and fencelines.
“Many growers are steering away from burning in order to retain stubble as part of their minimum-till cropping system,” Mr Wakefield says. “Some growers in the Yorke Peninsula are spending up to $30,000 a year on snail baits, so we ran this trial as a way to improve the effectiveness of this control option.”
He says growers often assume spreading snail bait requires the same machinery set-up as spreading urea. However, when the YPASG tested spreading bait as part of a separate urea spreading experiment earlier this year, the poor distribution results using the urea setting prompted this dedicated trial.
Armed with four different brands of spreaders (Amazone, Bogballe, Kuhn and Vicon) and two ute spreaders (C-Dax and Lehner), the group tested distribution of four common snail baits (Meta®, Metarex®, Slugger® and SlugOut®) – representing a range of pellet sizes and prices ($10 to $40 per hectare). The trial was run at Mr Wakefield’s property from 12 to 16 August, and involved the expertise of SA Research and Development Institute entomologists Greg Baker and Helen De Graff. The spreader settings were calibrated by Russell Nichol from the Australian Fertiliser Services Association, manufacturer representatives and University of SA engineer Dr Chris Saunders.
“The trial was not intended to pitch spreader brands against each other or preference snail-bait brands,” Mr Wakefield says. “Rather it was intended to achieve the most uniform bait distribution for each product and spreader available on the day, to assess what settings are required to achieve the best application rate.”
The trial compared the distribution of baits at different settings to identify the optimal settings on each spreader for spreading different snail baits.
“When compared with the recommended spreader setting for urea, the trial showed that all spreaders do not spread the same rate at the same settings. Snail baits spread at different rates to urea and each brand of bait had different spread characteristics. Growers are paying between $15 and $85/ha, depending on the bait, but may not be applying it effectively.”
Russell Nichol leads Accu-spread, a spreader testing and accreditation program run through the Australian Fertiliser Services Association. He has tested about 100 spreaders in the past year, and says many growers are surprised at the inaccuracy of equipment.
“The test involves running the spreader across 50 catch-trays in the paddock, to assess the accuracy and evenness of distribution,” he says. “Different products have different physical characteristics and spread differently, so it is important that growers get their spreader calibrated for snail bait. Knowing your fertiliser spread pattern and width of spread enables growers to optimise the performance of their machine for the best environmental and productivity outcomes.”
Entomologist Ms De Graaf says a consistent distribution of bait is paramount to reducing the impact snails can have on crops.
“There is very little evidence to indicate pest snails are attracted to snail baits, so it is essential to achieve a good, even spread of baits to increase the likelihood of snails encountering them,” she says.
The YPASG trial results will feed into a larger, three-year GRDC-funded project, which started in June 2013 and expands on a one-year scoping study (2012-13). It aims to improve the grain industry’s capacity to control snail and slug infestations and manage rapid outbreaks.
More information:Greg Baker, SARDI Entomology,
Helen DeGraaf, SARDI Entomology,
Yorke Peninsula Alkaline Soils Groups,
Russell Nichol, Accu-Spread program,
0418 505 002,
GRDC Project Code DAS00134
Region South, North, West