Pasture with dry patches

Hi! I live in Cantabria, northen region of Spain. This year we got an invasion of some kind of butterfly that went through most of our pasture in worm/ larvae form. I heard that if we are lucky and we get some frost they may kill the dormant larvae but is there something that I kind do? I plan to reseed with some pasture mixture to help next spring but was wondering if there are some eco friendly measures to avoid this pest.
Thanks!

Althea, I keep reading the title and your post so I must say I don't understand about the dry patches.

Did the larva kill those spots?

The only effective way I know to get rid of the larva is to hand-pick them and drop them in a pail of water to kill them.

Maybe spraying with a mixture or soap and water or a mix of 50/50 vinegar and water might work.