Slugs and snails
Slugs and possibly snails are attracted to the young foliage tops and young stems. They can be a bit of a pest due to the fact that celery needs to grow in very damp soils which may require regular watering.
Product Solution: Scatter Slug and Snail Killer, Slug Bait or Natria Slug & Snail Control thinly around plants you want to protect. Read pack instructions before use.
Cultural measures: Keep areas around susceptible plants clean and well cultivated.