I just found out my grapevines (2 of which already died) are infested with
Eurhizococcus brasiliensis, a ground pearl insect that attaches to the
root and suck the plant dry and inject poisons. It is endemic to southern Brazil and has no known solution. Chemicals aren't very effective and its sole predator is the larvae of a fly (and guineafowl, but they're not very useful as they only scratch the surface). It is dangerous only in its cyst and nymph stage, afterwards it develops into an ugly flying insect. Also, it seems it partners with
ants, that can transfer them onto healthy plants.
I understand few if any of you know this bug, but I have hope some permie-solutions you come up with or already know to deal with other root-dwelling insects will also be effective against Eurhizococcus.
Pictures (site in portuguese)