This is ghosting caused by Temporal Anti-Aliasing. It’s most prominent when you have an object moving accross a very noisy / detailed background. In your case the foliage appears noisy and makes the artefacts more visible. High-contrast backgrounds make it even easier to see (e.g, you foliage doesn’t match the colour of the terrain underneath it).
The solution is to either not use TAA (switch to FXAA in project settings, but it’s not as pretty), or to try to use less noisy scenes.