So far — no slugs. The first dahlia buds are opening to deep crimson blooms, and, so far, the leaves are  unmarked by slugs or snails. The decision to put each plant in an individual pot on the gravel path seems to have helped. As did Ken's double application of 'Nemaslug'.

Now, I must investigate the culprits that have left small nibbles all over the leaves of the teasel plants in the greenhouse.