Question
Our well established vinca minor is dying in large patches.
No sign of stem rot or insects; no dark spots on leaves.
Some area are in shade and some in partial sun but all areas are filled with dying patches.  Any ideas? Thanks

Answer
Hi Toni,

This is puzzling.  My first thought is that there is something interfering with the water uptake, thus the root systems must be affected.  There are many small mammals (moles, voles, etc.) that feed on roots.  There are also fungal root diseases that can affect plants in a very sporadic manner causing die back and patchiness.

Symptoms of root rot disease.  Shoot-tips of affected plants may wilt and die as the result of the rotting of the roots.  Vinca Canker and Dieback, and Root Rot occur in "patches" in a planting.  _Pellicularia filamentosa_ is the fungal species responsible for the root rot.  To determine whether this is the problem, lift the dying/dead plants from the soil and examine the root systems.  If you smell a foul odor, that is most likely the cause.  Remove all affected plants.  There is no effective chemical treatment as the fungus is completely beneath the soil.

The only way to control this is to remove the affected plants and clean up carefully.  You may have to select another type of groundcover if the problem persists.