Putting the plants in a tank with 10% bleach and water, or about 10ppm of PP for several hours will take care of the parasites on the plants. As for the rocks, unless they are coming over and being used in the stream with water flowing over them the same week that they are harvested from a stream, would not be an issue. Parasites need a food source, and drying out or away from the host for a few days will cause them to die of starvation.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard