Hi Lyssa, your Dahlias are in my opinion evening supper for those dreaded earwigs, we have the same problems here in UK and I can tell by the gnawed holes mid leaf that earwigs are the culprit.
If you look carefully into the middle of the flowers, you might disturb these pests, apart from eating the plants, these wee beasties also eat greenfly ect so there not all bad ha, ha, ha I here you say, but yes they are, I'd rather eat the darn greenfly myself than look at the foliage looking like a lace table runner instead of nice lush greenery.
I try to avoid sprays at all costs but I know some people cant go down that road and as far as I know, there aint any sprays specifically for earwigs so I can give the tried and tested things that works for me without spraying.
If you have a shreader for paperwork, then take a handful out of the machine, stuff it loosely into a small flowerpot and put this paper filled pot onto a garden cane directly above / beside the Dahlias in question or any other plant as earwigs like Roses, Delphiniums ect, (anything that they can hide inside the flowers or under foliage) the paper filled pot gives these insects a nice place to hide as the sun comes up in the morning, the bugs are night feeders and hide in daytime as birds, black rain beetles etc love these insects, when you go out in the morning to inspect the pot on the cane for these bugs, take a bowl / bucket of boiling water and just shake the paper into the boiling water and this is good-bye to the bugs, replace more paper and pop the filled pot back again for the next day.
The other way is to make a mix of washing up dish liquid soap and add a dash of cooking oil spray this on the FOLIAGE only, don't mess the flowers up with oily water. the bugs dont like trying to climb up stems that are greasy, I don't find that works for me but others say it does for them.
The 3rd and last thing is late evening, try tie a paper bag over the flower head, next morning remove the bag without allowing the bugs to escape and then burn the bag containing the bugs.
Yesterday while weeding a new flower bed, I disturbed a earwig nest just under the soil, The father took off ate great speed and the mother tried to protect her babies, (dozens of them) tiny little things, so they would mature in a few weeks and guess where they were heading !!!!!. Anyway I covered the soil back onto the nest and took the flame thrower to the area as there are no plants there YET !!!!.
Hope this helps you out a bit, these pests can totally destroy a whole load of flowering plants if left alone.
Best of luck. WeeNel.