Q.I have a blackberry with strange modules that look like tiny snails they have pus inside but don’t have crunchy shells and there
are hundreds of them on the main stem and ideas please I can send a picture if it would help
Certified GKH Gardening Expert
They appear to be a type of slug, which is, essentially, a snail without a shell.
This article will help you: https://www.gardeningknowhow.com/plant-problems/pests/insects/kill-garden-slugs.htm
This is a Scale pest. Isolate the plant from other plants.