Autumn baiting timely for snail control
GroundCover™ Issue: 138 January - February 2019 | Author: Rachael Oxborrow
Light showers and overnight dews will signal the start of ideal snail baiting conditions this autumn.
Small amounts of moisture can stimulate snail movement and baiting must occur while snails are active, but before they lay eggs.
GRDC investment is focused on improving baiting performance to reduce the impact of the four introduced snail species of European-Mediterranean origin that have established in southern Australia.
Snails can cause substantial economic losses through yield loss from feeding damage, field control costs, additional harvest costs, grain value loss and receival rejection.
Research conducted by the South Australian Research and Development Institute (SARDI) over the past three seasons has shown the reproductive organs of snails begin to mature from late March onwards and most reproductive activity occurs from late April to July.
SARDI entomologist Helen Brodie says bait efficacy is improved when soil remains moist for several days and temperatures are still warm. Baits trialled in temperatures ranging from 10°C to 22°C had greater efficacy at the warmer end of the scale.
“If growers are unsure whether snails are active then it is best to bait a small area and check for dead snails after a few days,” Ms Brodie says.
“Even if snails don’t look active during the day, slime trails across the soil surface can be a good indicator of night activity.
“Although it may be tempting to apply bait early in anticipation of a later rain event to activate snails, growers should be aware that metaldehyde baits will degrade if exposed to temperatures above 30°C to 40°C.
“Significant rainfall can also degrade bran-based baits.”
In addition to ensuring baiting is timed correctly, research by SARDI and the Yorke Peninsula Alkaline Soils Group has shown the importance of correctly broadcasting baits and getting spreaders calibrated for pellet size and density.
Ms Brodie says a minimum of 30 bait pellets per square metre and up to 60 pellets/m2 for high snail density situations should be applied.
“Higher rates may be needed in heavily infested areas, such as perimeters, fence lines or calcareous outcrops,” she says.
“Where current label rates do not permit this, a repeat application should be considered.”
Pellet densities for registered rates of commercial products are available in the SARDI snail and slug baiting guidelines brochure.
Baiting is recommended in conjunction with cultural controls during summer and autumn to reduce snail survival.
Cabling, rolling or burning, summer grazing and effective weed control can remove refuge habitat, which will increase mortality from hot, dry summer conditions. According to Ms Brodie, these efforts will also improve bait encounter rates, as a simpler environment with fewer obstacles has been created.
GRDC has invested in snail research across southern Australia and Western Australia that is investigating the environmental conditions that lead to feeding and reproduction. The work builds on that of previous investments and aims to help growers optimise the timing of their baiting programs.
The project is led by SARDI in collaboration with the University of South Australia, the WA Department of Primary Industries and Regional Development and involves several farming systems groups.
Ten field sites have been established across SA, Victoria, Tasmania and WA 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 behavioural patterns of snails and slugs in southern Australia and WA.
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