The GRDC fast tracks slug control trials

A one-year ‘fast-track project’ has been developed to evaluate the impact of a range of slug control practices to help growers avoid losses

Key points

  • Slug management is a key issue for growers in the high-rainfall zone
  • A new demonstration trial will test cultural and chemical control
  • The threat of slugs this season is still high, despite dry conditions

Right bait, right time, right rate – that is the message behind trials into slug control that will be conducted by Southern Farming Systems and IPM Technologies this season.

Finding the most effective way to control slugs has been a key problem faced by grain growers during wetter seasons of the past few years.

Slug management was raised as a top priority for research through the GRDC’s High-Rainfall Zone Regional Cropping Solutions Network – a group of grain growers, agronomists and researchers that provides feedback to the GRDC Southern Panel to inform research investment decisions.

In response, a one-year ‘fast-track project’ has been developed to evaluate the impact of a range of slug control practices such as stubble management, baiting, cultivation, sowing depth and rolling.

Southern Farming Systems (SFS) business manager Jon Midwood says slugs have been an ongoing issue for the high-rainfall zone for years but recent problems have been driven by climate and wet summers.

He says SFS agronomists believe that the slug problem has not gone away despite the dry spring and summer.

“The feeling is the deep-burrowing blacked keeled slug has gone down deep into the soil and might take longer to come back up to the top once there is some rainfall,” he says.

“The grey field slug will be there but numbers will be significantly reduced because they won’t have juveniles or eggs laid over summer, as has been the case in previous years.

Photo of a man inspecting a tile

Terracotta paving tiles can act as surface refuges for slugs and are useful for monitoring the number of slugs. Check the tiles early in the morning when it is still cool, but bear in mind the clumping behaviour of slugs and their dependence on moisture may mean that samples are not always an accurate representation of the total number.

PHOTO: Michael Nash

“We are looking at the products we have available to use to give growers advice so when those conditions come up again next time, we have the information on hand.”

Ten locations in western Victoria, from Hamilton to Geelong, are being assessed for slug numbers. Three locations will be selected where control methods will be tested over strips of one or two boomspray widths.

In the demonstration trials, four baits will be tested – three metaldehyde-based products (Metarex®, SlugOut® and Meta®) and an integrated pest management iron-chelate-based product (Multiguard®).

There will be single and double-baiting at average and higher rates where baits will be applied at sowing and then shortly after. The longevity of bait in the paddock will also be assessed, as well as baiting points per square metre.

Stubble management, rolling and tillage will also be demonstrated, and field days will be held later in the season for growers to see firsthand what has worked.

IPM Technologies’ Dr Paul Horne says the three key factors in slug control are time of planting, rate of bait and when and how it is put out, either in the row or on the surface.

“The purpose to the project is that we can show farmers there is a way to deal with slugs and it’s not by skimping on bait and putting it out too late,” Dr Horne says.

“We expect there will be a carry-over of slugs in paddocks from 2012, even with dry conditions. We can get control if we use the right bait at the right time with the right rate.”

The Agronomist

Photo of a curly haired man

Craig Drum

Craig Drum

Tatyoon Rural, part of Gorst Rural Supplies

Tatyoon Rural agronomist Craig Drum, based at Tatyoon near Ballarat in Victoria, has seen massive crop damage in his region during the past three years because of the perfect conditions for slug reproduction.

The Gorst Rural Supplies and Tatyoon Rural agronomy team ran a paddock demonstration trial to test a range of registered insecticides against current metaldehyde slug baits. They placed 144 concrete tiles across 10 hectares, and in the first count they found more than 2500 slugs under the tiles.

After 10 treatments were applied in different areas, they came back every week for four weeks to count the number of slugs. While there were fewer slugs in these later counts, the researchers did not find any outstanding alternative products to current baits.

Mr Drum says the trial showed the agronomy team that baiting is still the way to go but is best combined with cultural practices, such as cultivation to break up the egg bed, burning and rolling to reduce the slugs’ habitat.

“For minimum-till or no-till that doesn’t fit the mould, but if you are prepared to be flexible and work the paddock, it makes a huge difference,” he says. “In 2012, a huge area of land around here was worked because the year before slug bait costs were as high as $100 per hectare – that was a major blowout.”

Mr Drum says while the number of slugs is predicted to be lower this season, he is still expecting to see plenty in crops.

“We’ve learned it’s not a matter of waiting for the damage,” he says. “If we think the paddock will have slugs we are putting slug bait out straight after sowing and finding that’s as good a control method as any.

“At least slugs are not breeding over the summer like they have in recent years, which is a positive.”

The Grower

Photo of a man in a beanie

Chris Shady

Chris Shady

Skipton, Victoria

When it comes to slug control, Skipton grower Chris Shady reckons he has tried just about everything. In 2010 and 2011, when rainfall was 150 to 250 millimetres higher than the average 600mm, he lost entire paddocks to slugs and was baiting. He was not making any progress.

“Our bait decisions weren’t as informed as they could have been,” he says. “Now we have the benefit of hindsight and we put out test strips in a paddock to see if slugs are around.”

Mr Shady crops 1800 hectares south-west of Ballarat with his wife Karen and two sons, plus workman Graham Caldow and his parents Bill and Yvonne. The main crops sown are canola, wheat and linseed.

During March and April, he gave 700ha a light cultivation to help with slug control. In the past two years, 75 per cent of his country has been cultivated and some stubble burnt.

“Before this we were moving to no-till so the cultivating really goes against my grain and I would never have done that five years ago, but if we don’t do it, it’s asking for trouble. It takes time but it is the cheapest control option we’ve got,” he says.

“There’s been no eggs laid since October so that’s the best outcome for a long time. It was hopeless when they were laying eggs all through the year.”

The Shadys’ Skipton property received 25mm of rain in February and it did not take long before slugs were out, even with such a dry spring and summer. The family baited and killed eight slugs per square metre.

The land they crop near Carngham had been dry, with only 20mm since October. “Hopefully the slugs there will need a water bottle to get across the paddocks,” he says.

“This year we will be baiting at label rates with the airseeder at sowing and keeping tabs on numbers to follow-up bait immediately after sowing if needed,” he says.

“Our aim is to break that breeding cycle before sowing. Two years ago, the slugs starting eating cereals, which had never happened before, only some legumes. They had free range of the place for a year. We don’t want to go back there.”

More information:

Dr Paul Horne
0419 891 575

GRDC Back Pocket Guide, Slugs in Crops:

Slug Control Fact Sheet:

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GRDC Project Code SFS00023

Region South, North, West