This may shed some light on another mystery: Two of my grapevines are severely stunted, and one appears dead. More information here:
These vines were exceedingly vigorous the first two years. Initially I thought the sharp decline was due solely to mole damage and the weakened root systems allowing pests and diseases to take hold. However, I recall spraying concentrated dollar store glysophate around the base of the grapes the same time as the Peachtree mentioned above. In both cases, there were no roots visible on the surface, broken or otherwise. But there were surely broken roots under the surface in the mole tunnels. Is it possible the glyso could have leaked through the soil and been absorbed into the roots that way?