EPA sharply restricts consumer use of diazinon, nation’s #2 selling home and garden insecticide:
They heard they were going to stop selling Diazinon crystals about 15 years ago. So, I bought the last 8 bags my local retailer had. I used the last one a couple years ago.
Now, I spread DE around the dog yard a couple times a year.
I am more concerned about ticks than carpenter ants.
Carpenter ants are only an issues here in NH if you buy loose bark mulch in bulk from one of the local landscape companies. Now, I buy it bagged.