|Issue: September/October 2000|
Issue: September/October 2000
In This Month's Issue:
In September, NPARL welcomed plant pathologist Dr. Robert Lartey to its professional staff. Dr. Lartey, who is originally from Ghana, brings a broad background of research experience to his new position. Dr. Lartey obtained his Diplom Ingenieur in agriculture from the University of Kassel (Germany). After earning his master's degree in crop protection at the University of Reading (UK), Dr. Lartey obtained his Ph.D. in plant pathology at Auburn University in Alabama. His previous research interests include work on the biological control of Rhizoctonia solani on cotton, involvement in the discovery and molecular characterization of turnip vein-clearing virus, and biotechnological studies of viral infection in tobacco and Arabidopsis. At NPARL, his research objectives currently center on Cercospora beticola, the causal agent of Cercospora leaf spot of sugar beet. His approach to address the Cercospora problem is multifaceted. Dr. Lartey plans to identify and apply natural antagonists to control the fungus as well as use biotechnology to expand the understanding of Cercospora infection. He will also analyze variations in the incidence of Cercospora leaf spot under different irrigation systems.
Research Associate Dr. Darryl Jewett has identified economically important viral pathogens in nearly 40% of the Cardaria spp. accessions collected throughout the western United States during his research program over the past year. These viruses, which are transmitted by the green peach aphid, cause beet western yellows and potato leaf roll. These diseases plague field crops and orchards worldwide. Through collaboration with Pete Thomas (USDA/ARS, Prosser, WA), in August these viruses have been identified in Cardaria draba (commonly known as hoary cress), Cardaria chalepensis, Cardaria pubescens as well as in Cardaria hybrids. The finding that Cardaria spp may function as reservoirs for viral pathogens increases the urgency of finding economically and ecologically viable ways to control these weeds. Dr. Jewett's research on the noxious weed hoary cress, a perennial mustard native to Eurasia, aims to refine the taxonomy of hoary cress and closely related mustards. Hoary cress is easily confused in the field, presenting an obstacle to its management given that control strategies for many of these related mustards differ significantly. Improved understanding of hoary cress taxonomy, as well as its range and ecology, will mean more effective management strategies can be implemented. Dr. Jewett's program relies upon a combination of modern molecular taxonomy, as well as traditional morphological techniques. The cooperating taxonomist is Ihsan Al-Shebaz of the Missouri Botanical Garden in St. Louis, MO.
During the week of September 12, Ecologist Research Associate Dr. Kerri Skinner worked in Beltsville as a member of the Writing Team for the National Program 304-Crop Protection and Quarantine Action Plan for weed science. This Action Plan is a strategic planning document for weed science research for the next five years written in response to a list of 16 critical issues developed at the Crop Protection and Quarantine National Program Planning Workshop held in Dulles, VA during July 2000. Among the target issues are research efforts to increase biological control of weeds and to study the invasiveness of plant species, as well as efforts to increase interagency cooperation among participants. The finalized Action Plan, a compilation of the work of many ARS contributors, will be posted on the internet through the ARS National Programs website (http://www.nps.ars.usda.gov) at the end of October, where it will be available for comment by ARS scientists as well as by members of the public. Dr. Skinner, who serves as co-coordinator of the weed biology and ecology component of the Action Plan, was also invited to serve as facilitator at the National Program 304/305 Crop Protection (Insects and Mites) and Crop Production Workshop to be held in San Diego during the last week of October.
Entomologist Dr. Tom Shanower co-hosted a symposium entitled "Ecology and Management of Grass-Mining Sawflies" at the 21st Annual International Congress of Entomology held in Iguassau Falls, Brazil from August 20-26, 2000. This meeting brought together approximately 4,000 participants interested in all aspects of insect biology. Working in conjunction with Dr. David Weaver (Montana State University, Bozeman, MT), Dr. Shanower organized the symposium to bring together researchers working worldwide to understand sawflies, which are a group of hymenopterans that feed on grasses. Some species of sawflies have become important pests of wheat and barley, particularly in North America, China, North Africa, and Europe. At the symposium, Dr. Shanower presented a paper that reviewed previous biocontrol attempts for sawflies and described the current control efforts. He was also co-author of a paper summarizing foreign exploration for biological control agents for the wheat stem sawfly. Other ARS scientists presented papers at the sawfly symposium as well, including Richard Mankin (USDA/ARS, Gainesville, FL) and Kim Hoelmer (EBCL, Montpelier, France). The papers presented at the symposium will be published in the Journal of Agricultural and Urban Entomology.
In August, Research Insect Pathologist Dr. Stefan Jaronski completed a five-week study of ecological factors affecting grasshopper pathogens in the Delta Junction, Alaska agricultural area. In the Continental U.S., when infected by pathogens many grasshoppers increase their basking in sunlight and heat themselves above what the pathogens can tolerate ("Behavioral Fever"). The grasshoppers thereby limit the microbial pathogens' usefulness in controlling these insects on rangeland. In Alaska, reduced solar radiation and a greater proportion of cloudy days could potentially decrease or even prevent behavioral fever and thus increase effectiveness of microbial controls. Dr. Jaronski's experiments indicate that the Delta Junction weather patterns do limit effectiveness of behavioral fever in grasshoppers. However, the overall cooler weather and resulting lower body temperatures in grasshoppers in Alaska greatly prolong the time it takes for a pathogen to kill its grasshopper host, time during which the hopper continues to eat a farmer's crop. While in the Delta Junction area, Dr. Jaronski also surveyed local grasshopper populations for native pathogens in collaboration with Entomologist Dennis Fielding (USDA/ARS, Northern Plains Agricultural Research Laboratory, Fairbanks, AK), tying pathogen prevalence data with life table and key mortality factor analysis. This research will support the development of ecological management practices in Alaska to minimize crop damage from grasshoppers.
Insect Pathologist Dr. Stefan Jaronski hosted Molecular Biologist/Insect Pathologist Dr. Michael Bidochka and Laboratory Technician Mike Lavender of Trent University, Peterborough, ON during the week of September 18. These scientists are developing molecular techniques to identify fungal pathogens of grasshoppers. Through this collaboration, these scientists seek to refine a streamlined, polymerase chain reaction (PCR)-based method to more easily distinguish among the various members of the Entomphthora grylli complex than present methods allow. The E. grylli complex is an important mortality agent of grasshoppers on U.S. rangeland. Dr. Jaronski is studying the prevalence of these fungi and how its populations are affected by grazing practices and ecological factors. Availability of a reliable and rapid method to differentiate between pathotypes infecting field specimens will greatly enhance scientists' ability to determine the persistence and efficacy of fungal isolates released for biological control.