Ask Mr. Smarty Plants

Petroselinum crispum (parsley) is native to the middle Meditteranen region of southern Italy, Algeria and Tunisia and thus falls out of Mr. Smarty Plants' expertise in plants native not only to North America but also to the area in which the plant is being grown. From the University of Purdue, Horticulture here is an article on Parsley.

Now, to try and discover what is causing the death of your parsley plants. The bugs that you call "armadillo-like," we always called "pill bugs" in Texas.  But your description is very good because the scientific name of that bug is Armadillidiidae (whoo, hope we don't have to spell that again!). While they are visible around your damaged parsley plants, we don't think they are the cause of the problem but only an indication. The pill bug lives in moist, protected places, and feeds on mold and rotting vegetation. In other words, something else damaged your parsley and the pill bugs are just cleaning up.  From the University of Kentucky, more information and pictures.

We found this article on Parsley Pest Managment Strategic Plan and, while we didn't read the whole thing, we did find some indications of some pests that may be the real culprits. The top candidate in our mind is the Listronatus oregonensis, Carrot Weevil. Scroll down to Page 18 of the article for a description of the damage this critter does to parsley and see if it matches the damage in your parsley. From Ohio State University An Integrated Pest Management Program for Carrot Weevil in Parsley.

Since we are gardeners and not entomologists, you're on your own now.