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Eastern white pine (
) is the most widely distributed pine species in North America (1). It is also both economically and ecologically important as it is used in many forest products and it’s bark and foliage is used by wildlife species (1).
White pine is a critical associate of hemlock (
) forests in the Appalachian Mountains. As hemlock woolly adelgid (
) is killing hemlock trees, white pines have been virtually left as the primary canopy trees in many areas.
Since 2006, there has been an increase in observations related to white pine dieback in many areas in Georgia, Virginia, and West Virginia (2).
Similar issues have also been reported in Maine and
New Hampshire.
Symptoms of dieback include branch flagging, presence of cankers (especially around branch nodes), resin on cankers, and mortality of all tree diameter classes (Fig. 1).
A close examination of symptomatic white pines, especially cankers, revealed the
Fig. 1. Symptomatic white pine sapling. presence of a scale insect,
that appears to be feeding on trees (3).
Further, a number of fungal pathogens were isolated from cankers such as
spp.,
spp., and
, although the incidence of fungi and species varied across the region. We have now reported
present in many southeastern U.S. states (Fig. 2) (3).
Fig. 2. Current distribution of Matsucoccus macrocicatrices in the southeastern
U.S. From: Mech et al. (2013).
This discovery is novel because this scale insect had previously been reported only from the northeastern U.S. and Canada, and it has not been associated with tree dieback or mortality or fungal pathogens.
is known to have a symbiotic relationship with a fungal epiphyte,
, which was rarely collected in our samples (3).
A B
It has become critical to better understand the insect and fungal factors affecting white pine health to provide future management recommendations (Fig. 3).
Fig.3. M. macrocicatrices insect in canker (A), and C. pinea (B),
Mech et al. (2013).
1.
To determine the range and severity of white pine dieback in the southern Appalachians.
2.
To assess if various attributes of forest structure and composition may be affecting the dieback incidence.
3.
To determine relative contributions of scale insect and fungal pathogens to canker formations.
We have established 33 long-term plots in Georgia,
Virginia, and West Virginia. These plots will continue to be monitored to assess trends over time. An additional 40 plots will be established in the three states above, and North Carolina, South Carolina, and
Tennessee in the range of white pine (Fig. 4). Sampling in Georgia and South Carolina has already commenced (Fig. 5).
Fig. 4. Range of eastern white pine. Inset indicates focus areas for sampling.
Fig. 5. Current established sites in Georgia and South
Carolina.
We will establish three, 10 m radius plots in each stand. All stands will be at least 5 km apart, and all plots within each stand will be at least 50 m apart.
In each plot, we will assess the following forest characteristics:1) forest composition (overstory plants); 2) forest structure (basal area, tree density); and 3) topographic features (elevation, slope, and aspect).
The following white pine attributes will be measured in each plot: 1) DBH and height; 2) crown class, and 3) crown condition (Fig. 6). A 1-5 scale will be used where 1 would be a healthy tree, 2-4 would be a gradual thinning of the crown, and 5 would be a dead tree.
The number of symptomatic seedlings will be counted along a 1 m strip along each cardinal direction.
We will select four saplings per plot to tag and catalog proportion of necrotic branches (Fig. 7).
Outside each of the plots, we will harvest three white pine saplings to quantify canker number and size, number of scale insects, and stem surface area.
Canker tissue will plated on selective media to isolate fungal pathogens. Pathogenicity tests will be conducted, and if there are resulting cankers, they will be re-isolated.
Fig.6. Example of plot layout. Fig.7. Tagged white pine sapling.
Our goal is to better understand the extent and severity of white pine health issues in the southeastern U.S. Further, we intend to provide information about the nature of canker formations on these trees.
Field and laboratory assistance has been provided by many personnel in the Gandhi Forest Entomology Laboratory (University of Georgia); Dan Miller and Dale Starkey (USDA Forest Service); and forest managers at various national forests.
We are grateful for the funding provided by the USDA Forest
Service, Forest Health Protection, Evaluation Monitoring Grant,
Virginia Department of Forestry, and Daniel B. Warnell School of
Forestry and Natural Resources, University of Georgia.
1.
Wendel and Smith. 1990. Silvics of North America.
2.
Asaro. 2011. Forest Health Review, May 2011.
3.
Mech et al. 2013. Journal of Economic Entomology.