Post on 18-Dec-2015
The Effect of Arboreal Diseases on Hemlocks and Oaks in
Southeastern Pennsylvania
Aria KovalovichAcademy of Notre Dame
Over the last century, regions of the United States’ deciduous and
coniferous forests have been wiped out by pests and introduced
diseases
What is the prevalence of two common tree diseases, Oak Wilt and the Woolly Adelgid, in Southeastern
Pennsylvania?
Problem
Background Information – Oak Wilt
Oak Wilt is a fungus that kills deciduous Red and White Oaks.
Its spores are carried to freshly wounded or cut trees by beetles or the root grafts of another infected tree.
Once it has invaded, the Oak Wilt
fungus blocks the tree’s conducting (water) system and causes the leaves to brown inwards from the sides.
Background Information – Hemlock Woolly Adelgid
The Hemlock Woolly Adelgid is a soft-bodied, microscopic insect that was introduced from Japan and infests coniferous Eastern Hemlock Trees, which have no resistance to it.
The insects lay their eggs on the tree’s branches, and the newly hatched nymphs migrate to the young branches and settle at the base of the needles.
They feed on the stored starches that are critical to the tree’s growth and long-term survival by inserting their feeding stylets into the base of the needles, which turn grey and fall off.
The insects travel slowly up the tree, until the whole tree is infested.
This map shows that Oak Wilt originated in the northern central states and has since been
spreading eastward. (1996)
http://www.nrs.fs.fed.us/disturbance/invasive_species/hwa/risk_detection_spread/
This map shows that the Woolly Adelgid originated in the eastern states and has since been spreading
westward. (2010)
http://www.nrs.fs.fed.us/disturbance/invasive_species/hwa/risk_detection_spread/
Hypothesis
If oaks are surveyed within forests in eastern, central, and western parts of Chester County, Pennsylvania, then there will be a greater percentage of infected trees in the western forest than in the eastern forest.
If Eastern Hemlocks are surveyed within forests in eastern, central, and western parts in Chester County, Pennsylvania, then there will be a greater percentage of infested trees in the eastern forest than in the western forest.
Materials
Science Notebook Camera Pencil Car with Driver Calculator
Procedure
Drive to each park or forest. Observe each tree, identifying whether the tree
is an Eastern Hemlock or a Red or White Oak. If it is one of the subject trees, look for signs of
disease or infestation, such as peeling bark or dying branches.
If it is one of the subject trees, mark down which species it is, and whether or not it is infected.
Repeat steps 2-4 for each tree in a 60-acre area. Calculate the percentage of trees that are infected
for each part of Chester County.
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Nu
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er o
f Hem
lock
Tre
es
Western Forest French Creek State Park
Central Forest Black Rock Sanctuary
Eastern Forest Valley Forge National
Park
Name of Forest Surveyed
The Prevalence of the Hemlock Woolly Adelgid Across Chester County
Healthy EasternHemlocks
Eastern HemlocksInfested With WoollyAdelgid
This graph shows the number of healthy and diseased Eastern Hemlock trees surveyed within sixty acres of three different forests arranged from west to east in Chester County. Notice that
the Eastern Hemlock is a rare species of tree within the surveyed forests across Chester County, and that the Woolly Adelgid infestation is present within Chester County. This suggests either that the climate of Chester County is not conducive to the abundant growth of Eastern
Hemlock or that the population of the Eastern Hemlock has been essentially destroyed, in part by the Woolly Adelgid.
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20
40
60
80
100
Nu
mb
er o
f O
ak T
rees
Western Forest French Creek State Park
Central Forest Black Rock Sanctuary
Eastern Forest Valley Forge National Park
Name of Forest Surveyed
The Prevalence of Oak Wilt Across Chester County
Healthy Oaks
Oaks Infected With OakWilt
This graph shows the number of healthy and diseased oak trees surveyed within sixty acres of three different forests arranged from west to east in Chester County. Notice that Oak Wilt is prevalent in both the Eastern and Western forests, but has not infected the Central Forest. This suggests that Oak Wilt has not infected Chester County forests in a west to east pattern, thus indicating that the factors causing the spread of Oak Wilt are more complex than simple
directional movement.
Diseased Hemlock branches