European is tough but beatable. Now I did not scorch my boxes. But my bees didn't catch EFB from boxes they got it from comb, and then the dying hive got robbed out by the healthy hive next door and they caught it from HONEY...
I considered the radical burn the bees, but I had the state bee inspector come out and sample my hive and send larva samples to Belton. I began treatment for EFB as soon as I could get medicine, before I got the belton results. And my local mentor advised me to pull all comb and honey, so I did this too. Frames too, either burned or the plastic ones cooked in a solar oven then put in trash after melted.
But when it came to scorching the interior of the boxes, working alone, I didn't feel like I could do it without setting something afire in our severe drought, so I just solar ovened them and scraped off any comb first...