With autumn approaching, snails begin to lay their eggs. They lay these in the soil. A rainy autumn favours abundant egg-laying of the molluscs. It makes it easier for the animals to deposit their clutch when the soil is loose and there are already gaps in it into which they can creep to lay their eggs.
Loose soil with gaps in the earth is typically produced during autumn ground work, such as turning beds over or deep loosening with the aid of a cultivator. If you then find a clutch of eggs – identifiable as white to beige lumps of several eggs of approximately one millimetre each in size – collect them and dispose of them. Either spread them out on the surface of the earth, where they then dry out or are eaten by garden birds and ground beetles.
In addition, as far as possible, do not leave the garden soil in a cloddy condition. Rake it smooth after digging, which closes up cracks. As is well known, only heavy soil is left in clods over winter, so that the frost makes it smooth. You can also treat beds at risk from snails with large amounts of lime, for example with grained burnt lime, to combat the animals and their eggs. As burnt lime in particular is very caustic, observe the necessary safety measures (skin protection, eye protection, if necessary breathing protection against lime dust) when spreading. One alternative is agricultural lime, which is much less aggressive. Also note to what extent the plants on the bed or the cultures later planted in it are calcareous.
In the case of discernible snail invasion in autumn, it is essential, is in order to reduce egg-laying of these animals, to effectively combat the adult animals – with the familiar means and measures, from a snail fence to collection, from use of slug pellets to putting down threadworms which kill snails (nematodes, especially Phasmarhabditis hermaphrodita).
Tip: If you use slug pellets with the active agent iron-III-phosphate, do not be surprised if you do not find any dead snails in the garden. Unlike other active agents for slug pellets, which kill the animals by causing them to overproduce mucus, iron-III-phosphate causes the snails which have eaten it to crawl into the soil before they then die there - the snails bury themselves.