Your profile says you are using an AMD GPU. Is this right? I know of an Intel issue like this, but not an AMD. Make sure dolphin is using the AMD GPU.
If you are actually using an Intel GPU, start by trying to update the drivers. This bug was fixed in 2014, assuming your GPU was new enough to actually get the fix. If it wasn't, either try a different backend or try a build from here https://forums.dolphin-emu.org/Thread-4-0-1288-and-over-causes-sparkles-in-d3d
Another thread: https://forums.dolphin-emu.org/Thread-split-hack-to-fix-sparkle-issue-in-older-intel-gpus-in-d3d
If you are actually using an Intel GPU, start by trying to update the drivers. This bug was fixed in 2014, assuming your GPU was new enough to actually get the fix. If it wasn't, either try a different backend or try a build from here https://forums.dolphin-emu.org/Thread-4-0-1288-and-over-causes-sparkles-in-d3d
Another thread: https://forums.dolphin-emu.org/Thread-split-hack-to-fix-sparkle-issue-in-older-intel-gpus-in-d3d