Sponsored by the Michigan Forest Association and Michigan State University Extension

Something's Eating My Tree
Article #309 May 2020
By Bill Cook

The growing season is a time when trees leaf-out, flower, fruit, and add more wood to their diameters.  There are myriads of organisms that feed on this abundant growth.

            One of the most common questions that Extension foresters, and other service foresters, receive has to do with tree health, or more precisely, poor health.  Concerned people want to know what’s happening and what they can do to help the trees. 
            Each year, the environment is a bit different, which can favor, or discriminate against, tree pests.  For instance, long wet springs will favor fungal pests that damage trees and, conversely may help suppress insect outbreaks, such as gypsy moths.  Nature is not a static, unvarying thing.  Conditions are volatile and outcomes often difficult to predict.
            People can help forest health experts narrow-down specific maladies by first doing a bit of investigative work on their own, which can be fun, too.  Try to have as much of this information on-hand before calling or emailing for help.  Good pictures can be helpful. 

• First, and foremost, know the species of tree, or at least the genus.  A spruce is not a pine.  The differences among species are important.  Do your best to observe the leaves, twigs, buds, fruits, and other characteristics.  The U.P. Tree ID website can help with this.  So can a good ID book, such as “Trees of Michigan” by Linda Kershaw. 
• Note the approximate height and diameter of the tree.  Don’t try to estimate the age, unless you have an increment borer.  Fifty years is not old for many tree species.  Big is not necessarily older. 
• What kind of soil conditions?  Where is the tree located?  In a backyard?  Along a road or driveway?  In the woods?  Which county?  Tree pest communities vary geographically around the state.  Monroe County will differ from Gogebic County. 
• Are other nearby trees affected?  If so, are they the same species?  If not, then something’s up with just one tree, which is an important clue. 
• Where on the tree is the damage?  Trunk?  Branches?  Leaves?  It’s often easy to blame something easily seen, when the problem is actually something entirely different.  For example, ant colonies or woodpecker activity are secondary effects of advanced heart rot or presence of bark beetles, respectively. 
• If the problem is with the leaves, is there a pattern on the leaf?  For example, maple tar spot disease is very common and distinctive among residential Norway maples. 
• Assess the patterns in the tree crown.  Is the damage from the inside-out?  Outside-in?  Top-down?  Bottom-up?  With conifers, are the older needles affected first, or are the younger, current year needles? 
• If you can, look carefully at the damaged area.  Do you see small fungal fruiting bodies?  Any small webs, odd growths or bumps, or dried-up insect parts?  “Scale” insects form odd bumps that many people don’t associate with an insect.  For instance, the Lecanium scale was giving trees a lot of grief a few years ago. 
• When did you first notice the problem?  Spring?  Summer?  A continuation from last year or the year before?  Many people don’t notice crown damage until 30 percent of the leaves display symptoms. 
• Make a note of unusually wet or dry weather over the past few years.  The impacts of these weather patterns often have long-term impacts by reducing tree health.  Reduced health renders trees more vulnerable to insects and pathogens.
• Was there any construction or root compaction within the radius of the sick tree?  That radius extends a distance roughly equal to the height of the tree.  Lawn tractors on soggy soils can do a lot of root damage. 

            Before you contact that expert, become familiar with the handful of more recent forest pests.  Take a walk through the DNR Forest Health Highlights, found on their Forest Health webpage.  This is an excellent summary of major pests. 
            You can also poke around on the forest health module on the U.P. Tree ID website, which lists common ailments by species and/or genus. 
            Another important point is that urban and residential environments are very much different than those in wildland forests.  The wild is much healthier for trees. 
            Don’t be too surprised if foresters cannot identify all the tree maladies in urban and residential environments.  Foresters are trained to manage landscapes and populations of trees, not so much individual trees. 
            Individual tree care is more the realm of arborists.  The website for the International Society Arboriculture has a good “finder” directory for certified arborists.  That certification is important.  Also, many municipalities employ urban foresters that may be able to provide advice to homeowners.  There are also tree care companies that employ arborists or urban foresters.  Be sure to check qualifications, of course. 
            Lastly, many times there is little that a person can “do” about helping trees recover.  Making sure the tree has the right amount of water, at the right time, is often the best treatment and is one of the best preventative measures.  When treatments exist, they are sometimes expensive.  So, you’ll need to decide just how much that tree matters to you and, perhaps, how it might affect your neighbors. 

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TRAILER- This website was created by a consortium of forestry groups to help streamline information about forestry and coordinate forestry activities designed to benefit the family forest owner and various publics that make up our Michigan citizenry. This website is maintained by Bill Cook, Michigan State Extension Forester/Biologist. Direct comments to cookwi@msu.edu or 906-786-1575.

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