Little League: batter uses bat to put dirt on plate before every pitch
I've had two batters this year demonstrate this as a habit, I don't believe it's malicious or intended to make it hard to see the plate for the pitcher. It's not a protest. I think it's just a weird habitual thing they do before every single pitch. But I literally cleaned off the plate two seconds earlier, then he steps up and drags his bat across, pulling a sizable amount of dirt onto the plate.
So the next at bat when he gets up, did it immediately after I cleaned the plate again. I called time, cleaned the plate again (twice cleaned the plate before a pitch was thrown), and told him if he intentionally covers the plate with dirt I'll call a strike for batters interference in delaying the game.
He stopped, but I don't actually know what the right call is.
Has anyone else dealt with this? This is LL Majors division. Nothing in the rulebook directly addresses it that I've found.