Help ID yard pests
I live in Rosedale at Iliff and Lincoln and the flowers in my lawn are getting destroyed by a pest and I am wondering if you can help me identify so I can treat. I planted a bunch of perennials in the spring - rose of sharon, agastache, catmint, jacobs ladder, clematis - and they are full of holes and I have had to cut many of them to the ground as the small bit of the plant that is left looks like see through lace. Interestingly the pests are not touching my columbine plants. I see lots of small white flies in the air in my yard every morning and evening so I am wondering if they could be the culprit. I started using neem oil a week ago and that seems to be helping a little bit, but I'm worried that the infestation is so bad that its a losing game and I need to take more drastic action. I have spent way too much money on plants to see it go down the drain!
I also have a disease in my elm trees - I've been told it is elm leaf miner - and I am having those trees treated this month - not sure if its related. Please let me know if you have any suggestions!
Denver County Colorado
I suspect the culprits are slugs. They feed at night so you don't see them but they do a lot of damage. They thrive in moist conditions so they have been living easy with all the rain we've had this season.
Read this fact sheet for some ideas on how to control them: https://extension.colostate.edu/topic-areas/insects/slugs-5-515/