My chard was looking a bit heat stressed, but appeared to be surviving the summer. I was hoping for it to rebound once the weather cooled off in September. Saturday, we noticed that something was eating the leaves and saw many of the long black beetles, which I have tentatively identified as the Margined Blister Beetle. Good thing I didn't just squish them with my bare hands like I do stink bugs and squash bugs! Since it was raining Saturday afternoon, I did not try to treat them with anything. I dusted them with diatomaceous earth Sunday afternoon, but it rained overnight and is still raining today (Monday). I notice there are still blister beetles on the chard this afternoon. Any other ideas on getting rid of these guys?