Throw in a couple of drops of dishwasher liquid (Dawn) soap as it will act as a surfactant (allow Diatomacious Earth to spread and stick) on the leaves.
You will probably have to reapply after a moderate , to a heavy rain.
I also like the idea of a "trap crop" of radishes, myself.
If the radishes get to harvest, its a bonus/ if not harvestible, the flea beetles leave your main crop alone.
Thinking about the radishes. It’s so hot now, not sure they will do anything. My garlic/pepper spray recipe has some dishwashing liquid added to it along with onions.
I hate to use it, because it doesn’t distinguish between the good and bad bugs, but it does kill whatever you squirt it on. Not sure how long that lasts. Hope to do it in the PM and hoping that by the AM, it will be less potent.