Lichen won't harm the tree but could be sign of a bigger problem

Lichen won't harm the tree but could be sign of a bigger problem
Lichen does not harm trees, but an extensive spread of lichen on a tree can indicate a tree under stress for other reasons. (Ellen Nibali/handout)

It seems like the lichen on my tree exploded this year. It’s all over some branches, whereas it used to be only in random spots on the trunk. I’ve been told not to worry about your average gray-green lichen, but is there such a thing as too much lichen?

It’s true that lichen does not harm trees because, being an algae-fungi combo, it has its own chlorophyll and is just using the tree as support. However, extensive spread can be a symptom of a stressed tree. Not a cause.


The tree’s canopy may have thinned enough that the lichen is getting more sunlight, or the bark’s makeup has changed and now holds more moisture or provides better surface for attachment. At any rate, individual branches may be dying and need removal, or the entire tree may be in decline.

Keep an eye on it.

Please help! I can’t kill the insects that are biting me. I’ve had exterminators treat my house three times. I bathe and wash my hair every day. I’ve tried all kinds of creams and ointments. I took samples to my doctor on scotch tape, but he couldn’t identify them. They are invisible! Now they are starting to bite my spouse, so I know I’m not imaging this.

This does not sound like an insect problem. House pest insects are visible (with head, legs, etc.) either with your naked eye or an ordinary magnifying glass. Many conditions produce the sensation of insect bites, however. The sensations are real. Sometimes the power of suggestion can cause the same sensation in others in the household.

Here are things that can make us feel like insects are biting us:

  • Some drugs and drug interactions (i.e., antibiotics, antidepressant, sedatives)
  • Some infectious and non-infectious diseases
  • Recreational drugs (for example, cocaine and methamphetamine)
  • Some herbal remedies
  • Stress, anxiety, depression
  • Neurological disorders
  • Dry skin (especially in winter when furnaces blow dry air)
  • Air particles or dust, from construction, deteriorated upholstery stuffing, etc.
  • Physiological changes such as menopause
  • Pesticides (this is one reason you don't want to spray chemicals in your house, especially without getting a positive identification of the pest first)
  • Static electricity
  • Paper shards (sometimes called paper mites, though they are not insects)
  • Fiberglass pieces
  • Carpet fibers

Search ‘stinging and biting’ on the University of Maryland Extension’s Home and Garden Information Center website.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at Click “Ask Maryland’s Gardening Experts” to send questions and photos.