Higher than average rainfall through winter and well into spring this season may have increased snail and slug activity and this may continue well into harvest. Relative humidity, as well as temperature, appears to be an important factor for snail activity, which could assist growers to determine bait application timing. Research has shown that snails generally move down to the ground when humidity is greater than 90%, but during autumn, may respond to humidity at around 80%. Although the snails are moving, they may not be feeding, the movement being a strategy to rehydrate.
Research is showing that snails may become surface active after summer rainfall, but do not always actively feed at this time. Baiting needs to occur before they lay eggs and is more likely to be effective in March. Snails can start laying eggs in autumn once soil is moist, the timing of which varies between seasons. However, after a decent rain a sample bait may be applied to determine if snails are indeed feeding. Information gathered from this can assist in determining the necessity to apply bait across the entire paddock.
SARDI research has also shown that it is more effective to bait before seeding when the soil is barer and alternative food sources are few. In areas where snails present a major problem, a second application of bait is recommended at seeding, especially along the edges of paddocks where there is possible further movement of snails from weed refuges outside of the paddock.
When considering summer snail control, the decision to use cabling, rolling and windrow burning should be weighed against whether it is desirable to retain stubble. If burning snails is the chosen strategy, windrows should be set up at harvest. Retained moisture in windrows will attract snails over summer and the snails can be then burned with windrows when safe to do so. This strategy is not as effective for small pointed snails.
Summer weed control should be carried out after creating windrows to remove alternative habitats where snails can seek refuge and source moisture during the dry months. With the removal of weeds, the snails will be forced to remain in stubble and/or windrows where cabling, rolling or burning can be utilized.
Success with cabling or rolling in summer depends upon high temperature. Choose a day where air temperatures reach 40°C (ground temperature about 55°C); at these temperatures snails knocked to the ground will dehydrate and die. Take care to avoid causing fire when cabling.