Forest Resource Protection Forest Health, Insect & Disease Forest Fire Control Staff

This information on sugar maple health is from North American Maple Project plots in Vermont. Four indicators of tree health have been used to determine annual trends over the last 20 years. Tree vigor, crown dieback, foliage transparency and tree mortality are all measures of health that vary depending on site, stress levels, disturbances and year. The crown condition index combines crown health measurements into one number making it easier to compare annual tree health. The percent change each year is shown to reflect improvements or declines based on the long term average crown condition. For more information on regional NAMP:

• A history of the North American Maple Project
• Sugar maple management highlights for the region

Vermont Sugar Maple Health Results for 2008

This year was a tremendous year for sugar maple health. Sugar maple trees on NAMP plots had dense foliage with little new dieback, showing remarkable recovery from recent stress years. In 2008, 30 plot-clusters (5 plots per cluster at each site) were measured.

Of the 1,029 canopy sugar maples monitored, 96% were healthy (15% dieback or less) (Figure 1).

Figure 1.  Trend in healthy canopy sugar maple trees on NAMP plots. Health is based on trees with less than 15% crown dieback.

Less than 1% of trees had thin foliage (less than 25% foliage transparency) (Figure 2), a new record for dense foliage.

Figure 2. Percent of canopy sugar maple trees with thin foliage (foliage transparency >25%). In 2008 foliage was dense and lush (low foliage transparency).

There were 12 new dead trees, 1.2% mortality. An index of crown condition showed a 2.1% improvement in overall tree condition (Figure 3).

Figure 3. Annual change in the Crown Condition Index (CCI) shows improvements in sugar maple condition in 2008. Crown Condition Index includes dieback and foliage transparency. Positive CCI values indicate better than average crown condition.

The presence of bole damages likely to cause significant health problems was recorded for 21 types of injury. Only 45 bole damages were recorded for all sugar maples on all plots. The most frequent damages were broken bole, conks, and sugar maple borer (Table 1).

VT Department of Forests, Parks & Recreation, March 2009