We are certainly hearing about slug troubles this fall. With the cooler temperatures, slugs seem to be feeding incessantly. Slugs of course are most often problematic in mulched areas and thrive in high moisture parts of the landscape. The following is more information.
Most slugs have a single generation per year with overwintering eggs hatching in spring and slugs developing through spring, summer, and fall. As winter approaches, slugs lay eggs, which overwinter and hatch the next spring. Some adults can also survive over winter until next spring and resume feeding.
If slug problems are particularly bad, you might consider fall applications of metaldehyde baits. Such applications can be effective, but are not the most efficient use of these baits because some adult slugs may have already laid eggs and the chemical treatment might not contribute too much to reducing spring populations.
A final point worth mentioning in the struggle against slugs is that natural enemies have a lot of potential to contribute to slug suppression. Some ground beetle and harvestman (aka daddy long legs) species are voracious slug predators. Reduce insecticide use in landscapes to preserve these predators of slugs.
Adapted from an article in the Penn State Field Crop News.