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A 'menagerie' of tree health problems

Trees in a yard or plantation can have many different problems that stress, injure, or cause their rapid or slow demise.  The following true story of a tree health specialist's visit to a central Minnesota lakeshore property which illustrates a ?menagerie? of tree health problems.  The landowner had planted over l00 Scotch, Norway, and white pine seedlings in his large yard about l5 years ago. Here's what I found this fall:

  • Some pines with many light green or brown needles.
  • Stumps where dead pines had been removed.
  • Globs of pitch on the trunks.
  • Holes in the bark made by woodpeckers.
  • Mulch up to one foot deep around the trunk and extending about two feet out from the trunk.
  • Some pines leaning and loosely anchored.
  • Black pitch-infiltrated soil caked at the bases of several trunks.
  • Root systems that were gnawed.
  • Other trees were healthy and had excellent shoot growth for many years.
Normally, mulching is a good thing when done properly; here, it caused a problem.  Mulching had kept the ground around the trunk cool and allowed root collar weevils to destroy tissues under the bark that transported water, minerals and organic compounds up and down the trunk. Gophers had chewed away many roots. Northern pine weevils, bark beetles, and deep wood borers had overcome waning pitch defenses of pines stressed by root collar weevils and gophers.  Zimmerman pine moths had increased and added to conducting tissue loss under the bark at various heights on the trunks.

What probably triggered these tree health problems were the gophers and the mulching. The landowner believed mulching contributed to pine tree health by keeping the soil moist and cool.  What he didn't know was that this much mulch (fairly thick and up to the tree trunk) allowed the root collar weevils to become established. Root collar weevils like cool, shady environments at the base of their host trees.  If he had not mulched, and if he had removed the lower branches and raked away the grass and weeds, enough heat would have reached the root collar area to prevent the root collar weevils from becoming established. The landowner also was unaware that gophers could damage tree roots. They can do serious damage in the central part of the state. This misinformation led to a cascade of effects and a ?menagerie? of tree health problems.