What do you think it is? A blight?
Anyways, your praying mantis' look way different than in SW USA. They are solid green. Mostly from commercial shipments as I am sure they are not native. Now I feel guilty for buying them on your post about 3' tall wild growing carrots in Febuary😋
I read somewhere that this is African type... (mantis, not carrot :p). This one is brownish and I think it's smaller than the green one you talk about.