Grains Research and Development

Date: 01.04.2003

Slugs challenge farmers doing the right thing by the soil

Slugs love newly emerging plants

AS FARMERS have moved to conservation farming systems, some of the pests of crops are adapting and moving too.

Slugs are now the target for research initiatives across the southern cropping zone because of the damage they are causing, primarily to newly emerging plants. The campaign, supported by growers and the Federal Government through the GRDC, is being carried out by Victorian-based company IPM Technologies Pty Ltd.

Conservation farming, involving minimal or no tillage and stubble retention, is improving soil health and cutting costs for farmers, but it is also a system that provides habitat for slugs and reduces their mortality because less tillage is involved.

Paul Horne heads IPM Technologies and says there are about five exotic slug species in Australia that are pests in agriculture, the most common in studies so far being Deroceras reticulatum.

Slug

"Slugs are widespread in southeastern states but tend to be more of a problem in the higher-rainfall areas," he said. These pests live in the soil during the hotter months, emerging with rain in autumn to breed and feed. It is at this stage, Dr Horne said, that damage to newly emerging crops and pastures commences but feeding can continue during the colder months.

A long-time pest, slugs have not attracted a great deal of research attention until recently. Many graingrowers have been reporting significant damage to crops and spending large amounts on baits, which are the most widespread form of control, applied in autumn and/or spring.

"Baiting can be very efficient but baits do not seem to be giving the control that some farmers are expecting. Burning of stubble is used to remove their habitat but is not desirable for other reasons, while cultivation destroys their habitat," Dr Home said.

"As far as biological control is concerned, we have some beetles and predator earwigs that feed on slugs but we don't know enough about these predators and others — what they are, where they are, and how not to kill them when we are controlling other pests; for example, the red-legged earth mite.

"The research aims to find ways to better use the biological control agents we have."

Dr Horne said that his company will be working with farming groups to:

  • identify slug species present in various regions — control measures could be influenced by varying life cycles
  • collect information on the status of slug predators, given current farm management practices, and see if control measures for other pests need to be modified to increase the effectiveness of these predators
  • develop a method by which farmers can quickly and accurately determine the risk slugs posed to crops, and
  • investigate the timing and targeting of baiting to maximise control and also of cultural methods such as burning and cultivation.

Dr Horne said the intention is to establish field study sites in conjunction with farming groups and also use these for extension purposes.

"There are several reasons to be optimistic that effective control of slugs can be achieved. This will involve a combination of biological, cultural and chemical control measures."

Program 3 Contact: Dr Paul Horne 03 9710 1554