Snail control is best done on multiple fronts. Snails need humid places to shelter, such as among weeds and other vegetation and in tree guards.
Orchard floor management
Reducing where snails can shelter will reduce their numbers. Remove overgrown vegetation and weeds along fence lines. Keep the orchard floor tidy and weed free. The same orchard floor management used for apple scab control and light brown apple moth, that you may be doing soon, also reduces habitat for snails by breaking down leaves faster and reducing alternative food sources for LBAM.
Snails become more active at this time of year, after autumn rain. If chemical control is needed then this is the recommended time to do it, killing adults before they lay eggs. In spring, snail numbers are higher so although you may kill the same percentage of the population with baits the number of survivors will be greater. There is also a lot more alternative food sources around and greater plant growth for baits to get lost amongst, meaning snails are less likely to find and eat the baits in spring.
Copper sprays applied for disease control in autumn and winter should deter snails and even kill them. If applying copper check for its effectiveness on snail populations before applying snail baits.
Before applying any baits, monitor for snail numbers to assess their distribution in the orchard and the level of damage to make sure that an application is warranted. Baiting may only be needed in a small area of your orchard. Apply baits after rain when snails are more active. Baits are more effective when applied evenly across an area, rather than mounded, and the ground is clear of excess vegetation. The baits will break down faster under heavy rainfall and/or irrigation. Care should be taken when using snail baits as they are toxic to dogs, cats, children and some wildlife.
Other cultural control options to consider are abrasive or copper barriers and poultry.
Further information links
For further information refer to IPM for Australian Apples and Pears (pp152-154)
Or see factsheets: https://www.agric.wa.gov.au/pest-animals/snail-and-slug-control?nopaging=1
Article reviewed by Stephen Quarrell (Tasmanian Institute of Agriculture) and David Williams (Agriculture Victoria).