Foliage Culling in Ray Tracing Primary Rays?

I am working on a modified ray tracing pass based on the primary rays pass and I have discovered that foliage is culled at a very short distance as opposed to in a normal deferred rendering pass. I have played with various r.RayTracing.InstancedStaticMeshes settings to no avail. I have therefore assumed that modifications to the engine code will be required to make this work. Can anyone point me to where in the engine this foliage culling is performed for the ray tracing primary rays pass?