Research conducted by faculty, a student and an alumnus of St. Lawrence,
on the severity and extent of damage done to sugar maple trees by
tent caterpillars has yielded "surprising" results, according to a report
submitted by the team.
The research was conducted with the support of a grant from the 2004 Mabel and T. Urling
Visiting Assistant Professor of Biology William P. Rivers;
former biology faculty member Rebecca Y. Rivers; Jessica L. Henty '06, of Knoxboro,
NY; Jack Rowbottom '04, of Norridgewock, Maine, conducted the research and
have submitted their report, titled "Mapping and Monitoring of Tent Caterpillar
Populations in Commercial Sugarbushes," to the Merwin Rural Services Institute
(MRSI) at SUNY Potsdam, which administers the Walker Fellowship program.
For the past several years production from sugar maple trees (acer saccharum) in
northern New York has been hurt by drought, a severe ice storm and most recently,
by a large outbreak of forest tent caterpillars (malacosoma disstria). The
researchers proposed the study to map the extent of caterpillar damage across
St. Lawrence County and determine the relationship between caterpillar egg mass
density, percent defoliation and sap sugar content.
Surprisingly, they found within the maple stands a poor relationship between
egg mass density in the spring and percent defoliation later in the year. The
researchers give two possible explanations. The first is that old egg masses
were inadvertently included in the egg mass counts, and the second is that
defoliation estimates were not accurate due to error in equating canopy
openness with defoliation, since openness could be caused by factors other
than defoliation (for instance, branch dieback, the ice storm or the recent
In spite of this apparently poor relationship, they did find a significant
relationship between defoliation and sap sugar content. On average, as percent
defoliation increased from one tree to the next, the average sugar content of
the sap declined.
Using binoculars, hemispherical photographs and refractometers, the team
collected data on drought, a severe ice storm and an outbreak of forest tent
caterpillars from 70 trees located in two commercial sugar bushes in southwestern
St. Lawrence County and on a distinct northwest-facing ridge with a well-defined
field/forest edge dominated with sugar maple trees. During the course of
the study, one site was sprayed with Bacillus thuringiensis (Bt) in an attempt
to control the caterpillars.
The researchers found no significant difference in the amount of defoliation
between the sprayed and unsprayed sites, although they do not maintain that
spraying had no effect, since other site differences might have played a
Based on satellite images from 2003, the researchers found that within
St. Lawrence County in 2003, the greatest concentration of caterpillar damage
occurred along ridges at lower elevations. They suggest that analysis of soil
type, aspect and degree of forest fragmentation might reveal other important
key variables as well.
A complete report is available from Gail Samuelson, director of MRSI, at
(315) 267-3436 or William Rivers.
The Walker Research Fellowship Program was established in 1993 to capitalize
on one of the North Country’s greatest resources –– its institutions of higher
education –– to help solve the region’s most urgent problems. Administered
by SUNY Potsdam’s Merwin Rural Services Institute, the program is funded
through gifts from organizations and individuals and named for its primary
donors, T. Urling and Mabel Walker P'79 of Watertown.
Faculty from any of the 11 colleges and universities in Jefferson, Lewis,
St. Lawrence, Franklin, Essex and Clinton counties are eligible to apply
for the fellowship awards.
Posted: February 18, 2005