Mandatory drug testing would trim it even more.
This has been tried and failed. Low drug detection rates and the testing cost more than savings from dropping the (relatively few) detected druggies. More sophisticated and costly tests aren’t the answer and mj is certainly not going to disqualify in states where it is legal.
It is possible that certain subgroups of SNAP recipients have heightened rates of drug use but it wasn’t the case across the Florida sample.