Preservation vs Pestilence

Please see the below log snippet of a lvl 51 goodie outlander using the preservation power (helpfile also below) in an attempt to remove the corruption brought on by I assume the pestilence commune. Expected: Preservation would remove the corruption. (Corruption = Something seems horribly wrong with the plant life here.) Actual: Preservation does not remove the corruption. (Corruption = Something seems horribly wrong with the plant life here.)