Slugs on the rise: What the 2024 Riverine Plains survey tells us

Key messages

• Slugs have become a significant threat to productivity in the Riverine Plains region
• A 2024 Riverine Plains’ slug survey found that slug damage had increased over the past five years, likely in response to wetter seasons
• Slug management cost 33 percent of respondents between $1– 50/ha, while 56 percent spent $50–100 /ha, and 4 percent spent over $100/ha
• The survey revealed a high reliance on three insecticide groups — 4A, 1B & 3A — which are all disruptive to carabid beetles (predators of slugs)
  

If you’ve been feeling like slugs are eating more than their fair share of your crops lately, you’re not imagining it. The 2024 Riverine Plains slug survey confirms it – slug damage has been on the up over the past five years, and wetter seasons are likely part of the story.

The survey was developed to better understand current practices used by farmers, and to see if any patterns emerged. It also captured practices from 2023 — a particularly bad slug year.

Here are the key takeaways, plus a bit of extra context on what it means for farming in the region.

Slug damage is getting worse

Farmers across the Riverine Plains region (and beyond) reported more slug damage over the past five years compared to previous years. The trend matches up with the recent run of wet seasons which created perfect breeding conditions for slugs. They’ve also been turning up in new areas, like northern Victoria and the central slopes of NSW, and attacking crops like lentils that weren’t such a problem in the past.

Slug control costs add up fast

In 2023, 96 percent of respondents applied bait (leaving only 4 percent who didn't), but managing slugs is costly. In terms of bait expenditure, in 2023:

• 33% of respondents spent between $1–50/ha
• 56% spent $50–100/ha
• 4% spent over $100/ha

And that’s before factoring in the cost of re-sowing after a slug attack. Concern at the cost was evident, with one farmer summing it up perfectly: “constantly baiting isn’t sustainable.”

In 2023, large areas were also resown after being damaged by slugs, with 36% of respondents resowing 1–50 ha, 16% resowing 50–100 ha and one farmer having to resow over 100 ha.

Heavy reliance on a few insecticides

The survey showed most growers are using three main insecticide groups (4A, 1B and 3A) to control other pests but these chemicals are also hard on carabid beetles, one of the slug’s biggest natural predators. It‘s a reminder that pest control isn’t just about what you’re targeting, it’s also about what you might be knocking out along the way.

There are some alternatives available, and a softer insecticide option (Group 28) was used by 15% of respondents in our survey.

Confusion around farming practices and slug risk

Conservation agriculture practices like stubble retention and minimum till can create friendlier conditions for slugs, but they’re not the only factors at play. Some survey responses suggested uncertainty about how much burning or cultivation helps with slug control, and whether it’s the practice itself or the improved crop establishment that makes the difference.

Room for non-chemical control

The survey found there’s still a lot to learn (and share) about non-chemical slug control. While many growers graze residues, burn stubble, rotate crops or use tillage to reduce slug habitats, very few are rolling stubble, despite evidence this can help.

The bigger picture

Slugs are a costly and growing problem in the Riverine Plains region. The survey makes it clear that:

• The run of wet seasons has likely contributed to the increase in local slug populations, and  their appearance in new areas
• Baiting is expensive, and farmers are looking for alternatives to reduce cost and reliance on chemical control
• Integrated pest management — including crop rotation, stubble and tillage strategies, biological controls, and predator-friendly practices — can be useful strategies for long-term control.

The challenge now is building local knowledge, trialling more non-chemical approaches, and helping farmers weigh up the costs, risks, and benefits for their own paddocks.

Want to know more? Read the full article: Non-chemical control options for slugs: results from the Riverine Plains industry survey.

Acknowledgement

This survey was delivered through funding through the Agricultural Innovation Hubs Program, supported through the Victoria Drought Resilience Adoption and Innovation Hub, through funding from the Australian Government’s Future Drought Fund. Support was provided by collaborators including the Irrigation Farmers Network, Vic No Till, Birchip Cropping Group and Dr MA Nash.

For further information about the slug-related work Riverine Plains is doing, please contact Project Officer Sabita Duwal by emailing sabita@riverineplains.org.au.