Ph.D. - University of North Carolina, Chapel Hill, 1975
Professor Department of Biochemistry
West Virginia University
Robert C. Byrd Health Sciences Center
P.O. Box 9142
Morgantown, WV 26506
Phone: (304) 293-7758
Fax: (304) 293-6846
Email: mwimmer@hsc.wvu.edu
Research:
RESEARCH:
In general, my laboratory conducts research on the analysis and environmental fate of organic pesticides used against forest defoliators. Our main project over the past 7 years has involved diflubenzuron (trade name Dimilin) used extensively in Appalachian forests for control of the gypsy moth. My laboratory has developed a unique method for analyzing this pesticide enabling rapid and sensitive analyses to be done, important for the hundreds of samples in a thorough environmental fate study.
The approach takes advantage of the thermal breakdown of diflubenzuron in the heat of the gas chromatograph. Using deuterated diflubenzuron as an internal standard, and mass spectrometry to detect specific ions, analyses can be done without purification of leaf extracts, and with only partial purification of more complex extracts such as those from litter and soil. We have found diflubenzuron to be persistent in the forest ecosystem. An average of 40% of the original amount after spray is still found on leaves at leaf fall, and the pesticide is detected in ground litter for over 17 months post spray, with much added at the time of leaf fall from that remaining on the overlying foliage. It appears to be degraded as the litter decomposes during the hot summer months: none is detected in underlying soil, whereas one of its metabolites is found, primarily in litter and some in soil. We are beginning studies of a new pesticide, MIMIC, that is being developed for forest defoliator control.
The pesticide also appears to be heat labile, with fragments not detectable. Thus, we will be using our new electrospray mass spectrometer, which does not require gas phase ionization, to develope a selective method for analysis prior to analyzing field samples for MIMIC persistence similar to the Dimilin studies.
Selected References:
"Analysis of Diflubenzuron by Gas Chromatography/Mass Spectrometry using Deuterated Diflubenzuron as Internal Standard." Mary J. Wimmer, Robert R. Smith and Jeffrey P. Jones, J.Agric. Food Chem. 39, 280-286 (1991)
"Persistence of Diflubenzuron on Appalachian Forest Leaves after Aerial Application of Dimilin." Mary J. Wimmer, Robert R. Smith , Deborah L. Wellings, Steven R. Toney, David C. Faber, Jerry E. Miracle, Jason T. Carnes, and A. Ben Rutherford, J. Agric. Food Chem. 41, 2184-2190 (1993)
"Persistence of Diflubenzuron on Appalachian Forest Leaves in Stream Water." Elisabeth A. Harrahy, Mary J. Wimmer(*), Sue A. Perry, David C. Faber, Jerry E. Miracle, and William B. Perry. J. Agric. Food Chem. 41, 2191-2196 (1993)
"Long-term study of the persistence of diflubenzuron in an Appalachian forest after aerial application of Dimilin: effect of growth dilution on leaf coverage." Mary J. Wimmer, Robert R. Smith , Diane M. Hart, Jerry E. Miracle, Jason T. Carnes, Aaron B. Rutherford, Shital M. Patel, Ken E. Myers, Gary T. Haught, Mary Prince, Edward L. Andrada, Alfonso P. Austria, and Michael Miller. Environ. T oxicol. Chem., submitted (1996)
"Long-term Study of the Persistence of Diflubenzuron in an Appalachian Forest after Aerial Application of Dimilin: Retention In Ground Litter over Seventeen Months Post-spray." Mary J. Wimmer, Robert R. Smith , Diane M. Hart, Cecilio G. Delgra, Jerry E. Miracle, Jason T. Carnes, Aaron B. Rutherford, Shital M. Patel, Jamette R. Huffman, Edward L. Andrada, Ekachai Lucktong, Alfonso P. Austria, Parween Loynab, Ken E. Myers, Gary T. Haught, Raoul I. Tamayo, and Mary Prince. Environ. Toxicol. Chem., submitted (1996)
Mary Wimmer, Ph.D. 
In general, my laboratory conducts research on the analysis and environmental fate of organic pesticides used against forest defoliators. Our main project over the past 7 years has involved diflubenzuron (trade name Dimilin) used extensively in Appalachian forests for control of the gypsy moth. My laboratory has developed a unique method for analyzing this pesticide enabling rapid and sensitive analyses to be done, important for the hundreds of samples in a thorough environmental fate study. 
The approach takes advantage of the thermal breakdown of diflubenzuron in the heat of the gas chromatograph. Using deuterated diflubenzuron as an internal standard, and mass spectrometry to detect specific ions, analyses can be done without purification of leaf extracts, and with only partial purification of more complex extracts such as those from litter and soil. We have found diflubenzuron to be persistent in the forest ecosystem. An average of 40% of the original amount after spray is still found on leaves at leaf fall, and the pesticide is detected in ground litter for over 17 months post spray, with much added at the time of leaf fall from that remaining on the overlying foliage. It appears to be degraded as the litter decomposes during the hot summer months: none is detected in underlying soil, whereas one of its metabolites is found, primarily in litter and some in soil. We are beginning studies of a new pesticide, MIMIC, that is being developed for forest defoliator control. 
The pesticide also appears to be heat labile, with fragments not detectable. Thus, we will be using our new electrospray mass spectrometer, which does not require gas phase ionization, to develope a selective method for analysis prior to analyzing field samples for MIMIC persistence similar to the Dimilin studies.