Never seen critters like that. But I've used home-made brew like water with Dawn dish washing liquid,
a bunch of red pepper flakes & let it boil awhile & then let it steep awhile. I've sprayed this concoction
on vegetable plants & it either killed or kept away bugs feeding on them. Of course, we don't see too
many cactuses or cacti here in southwestern Pa. , so who knows if this will work on them.