My Supertunia Picasso In Blue petunia hybrid has started getting holes in the leaves or foliage. What do you suspect is abusing this

Question

and what should I do?

Answer 1

It's probably an insect problem, not disease. Potential offenders are caterpillars, beetles, or even slugs and snails. Look through the foliage and see if you can find the caterpillars or beetles. Those can be picked off and dropped in a bucket of soapy water. Or treat with Bt (Bacillus thuriengensis). If you see shiny trails, slugs are the pest. Surrounding the plant with sand might deter them crossing over to the plant.

https://www.gardeningknowhow.com/ornamental/flowers/petunia/problems-with-petunias.htm