According to Svetlana Micic, a GRDC-supported Department of Agriculture and Food WA entomologist based at Albany, the slug damage may increase and was difficult to detect when seedlings were eaten to ground level.

More obvious signs of damage are irregular pieces chewed from leaves and shredded leaf edges, according to Ms Micic.

"Slugs, which are hermaphrodites, meaning both members of a mating couple can lay eggs, usually emerge in paddocks with heavy soil types," she said.

"Mating usually occurs with favourable moist conditions after summer and eggs are laid into moist soils, usually in mid-autumn to mid-winter."

Ms Micic indicated that slugs can be difficult to find and their numbers under-estimated, as they hide under surface residue, clods or rocks during the day, but are active at night, especially moist, warm and still nights.

Fresh trails of white and clear slime, visible in the morning, indicate their presence.

Slugs comprise one pest that Ms Micic is researching as part of a GRDC funded project, 'Crop pest management farming systems in high rain-fall areas of southern Australia'.

According to Ms Micic, growers can gain an indication of slug numbers in a paddock by placing slug pellets beneath hessian, carpet squares or tiles placed on the soil surface.

Ten large slugs per square metre can cause significant damage to an emerging canola crop.

After a few days, slug numbers under and around each collection point should be counted.

"Now that canola has been seeded and germination has started, crops should be examined at night for slug activity," she said.

"The best time to apply pellets is early in the season after good germinating rains, as this is when slugs are emerging from their hiding places to look for food and there is little green plant material around to compete with baits.

"Late applications are less effective at attracting slugs as there is a lot of green material as an alternative food source.

"Large slugs are surprisingly mobile in moving to baits and plants."

Ms Micic recommended multiple baiting, rather than a single application at a high rate, because pellets could become covered by soil during rain and decay after wetting.

Growers should consider reapplying baits after significant rainfall events.