Sugar Maple – Value, Strengths, Threats and Resilience

By Tom Worthley, Assistant Extension Professor, UConn Extension

Hardly an autumn season goes by without numerous writers in magazines, newspapers and websites extolling the virtues of sugar maples for their foliar brilliance and colorful contributions to the Connecticut countryside. Shortly thereafter the late winter and spring can be relied upon to summon forth additional textual homage to sugar maple for nurturing our lives as New Englanders, feeding the woodstove fires to provide cozy warmth during cold evenings or the evaporator fires used to boil its sap, whether we participate actively in collecting, boiling and finishing maple syrup or are consumers. Summer arrives and eloquence is waxed once again as we read about maple shade-tree lined avenues of summer strolls or banks of fishing streams or woodland edges where we might while away our New England summer picking the season’s berries and enjoying them with pancakes and maple syrup.

UConn Extension Sugar Maple Program

Of particular interest within UConn Extension is the success of our own sugarbush operation this past spring. Under the expert guidance of UConn Extension Research Assistant Michael Palladino, a CT Certified Forester, the student Forestry and Wildlife Club enjoyed a successful maple syrup-making season. They upgraded their equipment and expanded the tapping operation to about 150 taps, collected sap throughout February and March and boiled it into high-quality maple syrup at the sugarhouse located near Farm Services on the Storrs campus. A large portion of their production was sold during a tour of the sugarbush off of Old Turnpike Road and the Sugarhouse in March, hosted by UConn Extension and the Forestry and Wildlife Club. An equally large portion of the production is being purchased by UConn Dining Services, for local consumption.

Late last summer, certain sugar maple trees were selected by Palladino and myself for removal in a thinning operation on other UConn Forest acreage. Trees were felled by participants during a UConn Extension workshop on chainsaw use and safety. During the fall semester, students working as part of the UConn Forest Crew drew the logs out of the woods and milled them into boards on the UConn Forest portable bandsaw mill. Part of this work was conducted during another UConn Extension workshop on small-scale lumber production using portable bandsaw mills in October that welcomed 45 participants. Graduate student Nathaniel Cyrus is a master’s degree candidate whose research is supported my grant funds. As part of his research into local forest products he has worked with the maple lumber, placing it in a solar-powered dry-kiln that was designed and built by students and is seeking out small-quantity local markets for its potential sale. We expect a portion of this UConn-produced lumber to go into the making of educational toys.

These are but a few examples of how the value of sugar maple is manifested in our daily life. And while I would like to discuss the myriad ways in which sugar maple is useful and valuable for everything from bowling pins to figured guitar parts, I have to admit it has likely been done already. An enormous body of text exists to remind us about how sugar maples are integral to the daily activities, community character and seasonal rhythms in our lives as New Englanders. Suffice it to say that I mourn them when they pass and miss them when they are gone. It is my fervent hope that sugar maple as a component of our landscape can adapt to the impending threats present in the environment from insects and diseases to changes in climate and weather patterns.

Tom teaching in woods

Tolerant of shade, able to live a long time, while producing prolific numbers of highly viable seeds, and fiercely competitive on good, fertile sites, sugar maple might just possess the characteristics it needs to continue as a key species in our forest ecosystems. That said, just like any other organism, sugar maple faces a wide variety and number of potential threats, both old and new that can affect its health, life, and very presence in our woodlands. Insects, fungus diseases and pollutants lead the list of concerns.

Threats to the Sugar Maple

The current headline threat to sugar maple in Connecticut is an insect currently causing damage to maples in Massachusetts called the Asian longhorned beetle (ALB). While not found in Connecticut yet, many folks are on the lookout for this non-native invasive pest that causes damage by boring through the woody portions of a tree. A large black and white insect with long antennae in the adult stage these insects can cause serious structural damage to trees and while they spread slowly, they can remain undetected for years. The Worcester, MA area is under quarantine while state and federal agencies try to eradicate the ALB population in there. Partially due to the presence of this pest, wood from Massachusetts is regulated and can only enter Connecticut after being inspected and issued a permit. Detailed information about ALB can be found at web sites hosted by the CT Department of Energy and Environmental Protection, CT Agricultural Experiment Station and USDA Forest Service.

Insect pests native to New England and co-evolving with sugar maple are not usually a serious problem, as the tree has developed defensive adaptations. But during times when conditions allow for population outbreaks, insects such as saddled prominent, forest tent caterpillar, maple trumpet skeletonizer and maple leaf cutter can affect growth and tree health. Most insect pests affect the foliage of sugar maples, and in turn can be preyed upon by birds and other creatures. ALB is the exception, being hidden in the tree and boring through the woody portions.

Various disease organisms can also affect sugar maples. Some can take advantage of stressed or weakened trees and some become problematic under certain environmental or weather conditions. Foliar fungi are always present in the environment, but excessively moist conditions; lots of rain or high humidity, during the growing season can give them an advantage. Anthracnose fungus can cause dead brown areas on leaves and tar spot is a leaf disease the starts as small black dots that expand and combine to form large, black thickened areas. Stem diseases such as those caused by Nectria or Eutypella fungi are generally manifested as cankers, depressed or sunken areas with callus tissue around the edges, or galls-raised bumps or out-growths on the bark. These problems affect the appearance, structural strength and value of trees but are not usually fatal.


More serious are various vascular diseases that can enter the tree through wounds to the bark, branches or roots that allow entry of fungal spores. These can affect the conductive tissue and woody portions of the tree and can result in trunk rots, stains and hollow places. Otherwise healthy trees might have the ability to internally seal off or compartmentalize minor wounds but the damaged portion stays with the tree for the remainder of its life. A common killer of shade trees is verticillium wilt, a fungal disease that gains entry to the tree by means of damaged roots.

Perhaps it is apparent that the relative resistance or susceptibility of maples to disease and insect threats can be related to other stresses to which a tree is exposed, such as wounds, soil compaction, flooding or overcrowding. As stated earlier, sugar maple is extremely competitive on a good site and within that narrow range of conditions can out-compete or out-last just about any other tree in the woods. But sugar maple is also sensitive to slight changes in that ideal balance of site conditions, and certain changes can cause it to rapidly lose its competitive ability. A heretofore healthy shade tree subjected to soil chemistry changes from road salt, fertilizers and pesticides, soil compaction, over-mulching or the like can become susceptible to other disease problems and suddenly appear stressed. Air pollution, digging in the vicinity of the root system, livestock grazing, acid rain and chemical spills are all examples of environmental factors that can result in stress conditions for sugar maples in both urban and woodland settings.

Sometimes maples appear to decline and there doesn’t seem to be a single identifiable reason. It is not unusual that several of the factors mentioned above can be operating in combination, causing incremental stresses and resulting in trees or stands exhibiting reduced twig and foliage growth, early fall coloring, crown dieback and other symptoms of a condition called maple decline.  For example, a serious drought or an insect defoliation can cause a tree to use up nourishing compounds stored in reserve, leading to internal chemical imbalances and increased disease susceptibility. A broad-scale stress factor such as air pollution, acid rain or severe drought can result in landscape-scale maple decline.


Solutions for the Sugar Maple

So what can we do? The answer to that question is more about things we should not do. Beginning with an understanding that our favorite trees can be subject to numerous threats and stresses, it’s helpful to know that they have internal defenses that work to protect the tree most of the time. We can help by not adding to the stress load.

  • Avoid activities that can result in changes to soil structure and chemical balance-be careful with de-icing salt and chemical fertilizers.
  • Avoid soil compaction and root and stem wounding by logging, farm and lawn equipment. Graze livestock elsewhere and don’t over-tap.
  • Burying root systems under too much mulch, retaining walls and pavement can facilitate the entry of injurious diseases and insects.

Be aware that sugar maples can be quite robust, but are sensitive to changes.  If we control those potential stresses that are within our ability to control, perhaps our sugar maples can take care of the rest and be there to provide benefit and enjoyment for many seasons to come.

This article is a revision of an article that first appeared in Connecticut Woodlands, Winter 2013 issue.