Ok, yes I bit you are beginning to itch when you think about the topic of lice. But, do not fear you really have nothing to worry about when it comes to bark lice.
First things first, this lice does not transfer to humans or animals. They actually provide a service to the trees that inhabit. While you may not notice them on your tree bark, you will notice the web that they spin. It can cover the bottom of the tree along with the lower branches. The purpose of this webbing is really not fully understood but you will find these tiny insects living in the web they have spun. Their physical appearance will remind you of aphids due to their small size. They have long antennas on their heads and when they are not using their wings they fold them up over their heads so they look like hoods.
As far as their purpose in nature, they help the tree by removing dead material, fungus, algae, and mold. They do not cause the tree any harm except the appearance of the webbing but……..as the growing season comes to a close and the winter winds blow, the bark lice does something interesting. They eat their own webbing and do not appear again until the warmth of spring blows back in. Once that happens, the process begins all over again.
Now, one may be wondering about control. I mean, this is a pest, right? Well, this little insect does not harm any plant material and in doing so there really is no need to consider any type of chemical control. On the other hand, some gardeners will spray the area with water to break up the webbing in hopes of killing the bark lice. While this approach will destroy the webbing, the insects will rebuild and you will have the same problem or more. The hard spray that will be required to destroy or at least tear up the webbing can also cause bark damage, which is a welcome mat to pests and plant disease. At the end of the day, the best technique is to just let things be and realize that admiring nature’s work is finest thing we can do as gardeners.