Dr. Robert Mathiasen (retired) was Professor of Forest Health in the School of Forestry at Northern Arizona University, Flagstaff. He received his Ph.D. in plant pathology from the University of Arizona in 1977, an M.S. in botany from Colorado State University in 1974, and a B.A. in biology from California State University, Stanislaus in 1972. He has studied mistletoes in the United States, Canada, Mexico, and Central America since 1973 and published more than 50 professional scientific and extension papers on dwarf and leafy mistletoes. His research has primarily concentrated on the impact, ecology, and taxonomy of dwarf mistletoes. He retired from Northern Arizona University in 2019 after serving in the School of Forestry for 23 years. Before that, he worked as a forest pathologist for the Idaho Department of Lands in Coeur d’Alene, and prior to that he was a plant pathologist with the USDA Forest Service, Forest Pest Protection Branch in the Intermountain Region. He worked under the direction of Dr. Frank G. Hawksworth, who was considered the world’s leading authority on dwarf mistletoes until his passing in 1993.