The rest are underground digesting food, feeding on rootlets or just beating the heat. Fisher has found slugs as deep as three feet down in soil crevices. The best time to set out slug bait is in September or early October, after the first few showers but before the winter monsoons begin. This is a time when adult slugs come back above ground to actively feed and to seek mates. Mature slugs will readily eat baits, and it is possible to substantially reduce the breeding population before egg-laying begins.
Baits are less effective in winter and spring for a number of reasons.
Slugs will have laid tremendous numbers of eggs by winter. Many eggs will hatch. Younger slugs are not as readily attracted to the baits as the older slugs. Low winter temperatures and rains discourage bait seeking by slugs of all ages. Consequently, most baits applied in winter and spring are degraded by the weather rather than consumed by the slugs.