Thank you for your question. The only controls for millipedes are those to rid homes of them, where they become pests. In the garden, they are valuable 'recyclers,' and are helping break down organic matter to provide nutrients to your future garden. They will leave the lasagna beds when it gets too cold or wet. Here is an Extension article about them: https://www.extension.uidaho.edu/publishing/pdf/CIS/CIS1170.pdf Good luck!