Snail control – key strategies and where to next

Take home messages

• Timing and persistence are the keys to managing snails effectively
• Ensure good summer weed control and early baiting in autumn
• The ‘Nail the Snails’ management guide is now available
• Research is developing new tools for snail monitoring and management

Timing is key to managing snails

Managing Mediterranean pest snails remains a difficult and costly task for growers in snail-affected areas. There is no silver bullet control method for snails. Integrated snail management, coupled with good timing and persistence, is the key to effective snail control.

Getting the basics right is important. The key strategies are:

• Practice farm hygiene to prevent snails spreading to new areas (on infested harvesters, vehicles, or fodder)
• Control summer weeds to remove refuges
• Use physical controls to kill snails in summer (chaining, cabling, rolling)
• Bait early in autumn before snails lay eggs
• Burn stubble if needed
• Clean infested grain with screen cleaners and snail crushing rollers

These strategies suppress round snails effectively, but conical snails can be more difficult to manage. Investment bodies and researchers are aware of these challenges. New GRDC and SAGIT investments, led by SARDI working together with a range of research partners, are working towards finding new technological solutions for snail monitoring and management.

This paper briefly highlights key control strategies and current research that is working to improve snail management.

Why were snail numbers high in spring and summer 2022/2023?

Many growers faced higher than usual snail numbers during the harvest of 2022/2023. Unfortunately, there is little understanding of the factors that drive higher snail populations in some years, making prediction difficult. However, weather plays a central role.

Late winter and spring 2022 were wetter than average in many coastal regions of SA, with rainfall deciles above eight recorded all months from August to November (Figure 1). Snails start breeding in autumn and typically lay most eggs by early winter. It is likely that the wet spring allowed breeding to continue longer than usual, and/or increased the survival and growth rates of juvenile snails.

Figure 1. Monthlyrainfall deciles during winter and spring 2022 (source: adapted from the Australian Bureau of Meteorology, ).

Management tips

All integrated management strategies outlined above work together to suppress snail populations and are explained in detail in the Nail the Snails guide (see below).

To improve snail suppression in the Eyre Peninsula region, the need for good summer weed control and effective baiting (timing, rates, and application) is emphasised here.

Control summer weeds

Green weedy refuges keep snails hydrated and healthy over summer, increasing the problem in subsequent crops (Figure 2). Controlling summer weeds can reduce the over-summer survival of snails by 50% or more. Weeds should also be controlled before any other control operations (such as cabling, chaining, or burning) to maximise efficacy.

Figure 2. Lincoln weed, horehound, onion weed, and any other green weeds, harbour many thousands of snails in summer (photos: Kym Perry).

Bait snails before they breed

Baiting is an essential part of integrated snail management. Baiting should occur around early autumn to kill snails before they breed. Tips for effective baiting:

Apply bait at the right time

Apply bait around early autumn, as soon as snails commence moving and feeding, at the end of their summer dormancy. Snail movement is greatest when relative humidity exceeds 90% (often overnight). If both conical and round snails are present, consider baiting again around sowing time to target later-emerging conical snails. Baiting after early winter is less efficient. Cease baiting at least 2 months prior to harvest. There is nil tolerance of bait contamination of grain.

Apply and re-apply bait to achieve enough bait points

Always applyyour selected bait product according to product label directions. Pellet densities above 30 per m2 maximise the chance of snails encountering pellets. Consider the pellet density (per m2) when applied at the label rate (kg/ha) – refer to the product selection guide in the Nail the Snails guide (page 26). Re-apply the bait product as required to kill snails. Re-application may be needed in areas of higher snail density, such as fence lines.

Broadcast pellets evenly using a calibrated spreader

Uneven spread can drastically reduce bait performance. Calibrate your spreader for your selected product and drive at pass widths no wider than the effective spread width.

Bait mice before baiting snails

To avoid mice consuming snail bait.

‘Nail the snails’ management guide available

A new snail management guide is now available: Nail the snails: A practical guide to integrated snail control for Australian grain growers (see Useful resources). This guide is the second edition of the Bash 'Em Burn 'Em Bait 'Em snail management manual.

Snail research news

There are two projects currently focused on improving snail management:

• ‘More effective control of pest snails in Australian grain crops’ is a 4-year (2022–2026) GRDC-invested project led by SARDI, and working together with University of Adelaide, University of South Australia, CSIRO, DPIRD, Data Effects and Molluskit. The project is investigating new technology for snail monitoring and management, such as automated stations for monitoring snail movement, ground-based AI vision for counting snails, electrostatic separation of snails and grain, biocontrol, and snail attractants and barriers. Listen to the Nail the Snails podcast for more information (see Useful Resources).
• ‘Revegetation for enhanced biocontrol of pest conical snails’ is a 3-year (2022–2025) project led by SARDI with investment from SAGIT, GRDC and Viterra, working together with Trees for Life. The project is setting up long term research and demonstration sites on Yorke Peninsula, with border plantings of native plants, to investigate whether providing flowers in spring and summer can boost parasitism rates of conical snails by the parasitoid fly, Sarcophaga villeneuveana. In 2021/2022, SARDI performed releases of the fly on western Eyre Peninsula to establish local populations that can attack pest conical snails.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC. The author would like to thank them for their continued support. The author also thanks SAGIT and Viterra.

Useful resources

Nail the Snails: A practical guide to integrated snail control for Australian grain growers.

GRDC Podcast: Nail the Snails – with Kym Perry.

GRDC Slugs and Snails page

Contact details

Dr Kym Perry
SARDI Entomology Unit
08 8429 0738
0421 788 357
kym.perry@sa.gov.au