This kind of bug often stays on the back of stems and leaves and does not move. They absorb nutrients from the stems and leaves of plants, and at the same time secrete a sweet liquid to attract ants and fungi. Its pest principle is similar to that of aphids. A large number of barnacles will quickly kill plants. Fortunately, this worm is large, easy to find and easy to remove.
How to identify barnacle scale insects/scale insects?
This kind of bug often stays on the back of stems and leaves and does not move. They absorb nutrients from the stems and leaves of plants, and at the same time secrete a sweet liquid to attract ants and fungi. Its pest principle is similar to that of aphids. A large number of barnacles will quickly kill plants. Fortunately, this worm is large, easy to find and easy to remove.
The bugs gather on the stems and leaves, and once they find a suitable location, they stop moving.

This kind of bug is not only white, but also red.

There are also variegated ones, larger in size.

If you see white crawling everywhere, they are not scale insects, but whiteflies.
Solution
The method to solve this pest is the same as that of aphids. For details, please refer to Weed Grow Lesson 22: How to identify and treat cannabis killer aphids?
It is not difficult to control scale insects. The insects are large in size and look obvious. If there are only a few, they can be removed by hand. Insecticides that can remove aphids can remove scale insects. Always pay attention to the stems and leaves of the plant, scale insects will not develop into a fatal disaster.