When trees and shrubs decline in the landscape, the cause is often thought to be one of the pathogenic fungi or bacteria seen growing in branch and twig cankers. But when one of these pathogens is observed, is it always the cause of the plant’s demise? As a plant disease diagnostician, one is constantly faced with having to solve a mystery. What happened to the plant and when did it happen? Was the tree unknowingly murdered, or did it die of natural causes? A good diagnostician, like a good detective, needs to ask the difficult questions.
So we have the evidence: the tree is declining and about to die. Weakly pathogenic fungi are proliferating on the dead twigs and branches. Let’s begin the interrogation.
Did the tree decline due to lack of space for the roots to grow? Was there a witness to the digging of the planting hole? Was the planting hole dug much wider than the size of the root ball? Was the soil that was put back into the hole different from the original soil dug out? Did root rot occur because the planting hole was poorly drained? We all know that at planting, it is best to use the same soil that came out of the hole to backfill around the root ball.
Trees often decline because the tree was planted too deep. When the tree was planted, were flaring buttress roots at the base of the trunk observed? Was the soil from the nursery brushed back to expose the buttress root flare at the top of the root ball? Was the tree set so deep that the root flare was covered? Where were you at planting time? What did you know, and when did you know it?