Richard E. Johnsen

Associate Professor of Entomology

B.A., Biology, St. Olaf College, 1957, Northfield, Minnesota
M.S., Entomology, Chemistry minor, Iowa State University, 1959, Ames, Iowa

Ph. D., Entomology, Biochemistry minor, Iowa State University, 1962, Ames, Iowa

Research Interests

Persistence of Pesticide Residues: Transport, Fate and Effects We are currently working on the ground water pollution potential of soil-applied insecticides. We are studying two organophosphates, a carbamate, and a pyrethroid and their movement and degradation in three typical Colorado soils. This laboratory study involves the use of soil columns treated with individual insecticides followed by the periodic percolation of water through the soil profile. The percolated water is collected and processed through an analytical scheme for the insecticide and metabolites by gas-liquid chromatography. This study should enable us to determine the relative pollution potential of these insecticides.

A second project involved the determination of toxicity levels of a number of insecticides to both an insecticide-susceptible and an insecticide-resistant strain of the green peach aphid (Myzus persicae). A number of potential insecticide synergists were tested in combination with individual insecticides to determine if these synergists would be useful in overcoming the resistance problem. These studies have shown that these synergists can be very effective in reducing the resistance level of these insecticides.

Other recent projects include the determination of the residual persistence of chlorpyrifos on alfalfa in Colorado, the persistence of four pyrethroids on alfalfa, and use of a UV sunscreen to retard solar degradation. A continuing theme in our work is the use of and development of analytical protocols in the determination of pesticide residues.

Selected Recent Publications

Remington, T., Peairs, F., Pilcher, S., Meyer, W., and Johnsen, R.E. l991. Nontarget effects of chlorpyrifos and disulfoton aerially applied against Russian wheat aphid in Colorado winter wheat. In Proceedings of the 4th Russian Wheat Aphid Workshop, Bozeman, Montana, October 10-12, G. Johnson, Ed.

Al-Aboodi, A. and Johnsen, R.E. l99l. Synergism of organophosphorus and pyrethroid insecticides in the green peach aphid. Entomological Society of America, Annual Meeting, Paper Presentation, December 8-12, l991, Reno, Nevada.

Johnsen, R.E. l99l. Phorate use on beans. In The Biologic and Economic Assessment of Phorate and Terbufos, M.S. Fitsner, J.S. Bowman, and H.J. Stockdale, Eds, National Pesticide Impact Assessment Program, U.S.D.A. Technical Bulletin 1785, l3-16.

Remington, T., Peairs, F., Meyer, W., Rudolph, J. and Johnsen, R. l989. Nontarget effects of aerially-applied Russian wheat aphid insecticides in Colorado. In Proceedings of the 3rd Russian Wheat Aphid Conference, Albuquerque, New Mexico, October 25-27, l989, pp. 67-70.