Influence of Crop Rotation and Cover Crop on Fusarium Head Blight of Wheat

Fusarium head blight (FHB) of small grains tends to be associated with certain environmental conditions, especially rain-induced wetness periods occurring near anthesis. A Geographic Information System-based model simulation which incorporates 4km resolution weather radar (NEXRAD)-derived precipitation estimates into a crop canopy energy balance-based scheme to estimate wetness duration periods for small grains on the 4 km spatial scale has been developed and initially tested, with promising results. Errors found in the NEXRAD precipitation estimates analyzed during the first and second years of this project with Michigan precipitation data were less pronounced than previous studies, with 96.3% of the precipitation-hours across the state of Michigan during the 1999 and 2000 growing seasons correctly classified and an overall mean bias and mean absolute precipitation differences of -1.6mm and 2.3mm respectively. An initial validation of simulated leaf wetness duration in 6 wheat field sites in Lower Michigan at head height during June and July of the 2002 growing season resulted in mean differences of -0.2 hours and mean absolute differences of 3.4 hours over 116 separate events associated with dew, precipitation, or both. Mean differences and absolute differences for events associated with precipitation only or with precipitation and dew were +1.5 hours and 3.7 hours, respectively, indicating a slight tendency for overprediction. In an effort to better parameterize the wetness duration simulation including evaporation rates of dew and total intercepted precipitation, a field study began in April, 2002 with greenhouse flats planted with spring wheat in individual 10cm pots. Following heading, the flats were monitored with a weighing lysimeter over time, providing estimates of plant evapotranspiration, dewfall, and interception of precipitation. Preliminary results from these data suggest a total nightly dewfall ranging from 0.0-0.3mm. To study rainfall interception, wheat heads at the flowering stage were cut and collected from extra plants in the flats and mounted on 30 cm long, 0.1mm diameter steel wires. The heads and steel ‘stems’ were in turn mounted on a heavy steel wire frame which held the mounted wheat heads and wire in a fashion similar to that grown in the field. Rainfall interception totals on the order of 0.1mm to 0.3mm were recorded for 11 events. The canopy interception was observed to be associated with the drop diameter of precipitation, with less canopy interception occurring with large droplet diameters and vice versa. 2002 National Fusarium Head Blight Forum Proceedings 133 Epidemiology and Disease Management A SECOND GENETIC MAP OF GIBBERELLA ZEAE R.L. Bowden1*, J.E. Jurgenson2, J.K. Lee3, Y.-W. Lee4, S-H Yun4, K. Zeller3, and J.F. Leslie3 1USDA-ARS Plant Science and Entomology Research Unit, Manhattan, KS 66506; 2Department of Biology, University of Northern Iowa, CedarFalls, Iowa , U.S.A. 50614; 3Department of Plant Pathology, Kansas State University, Manhattan, KS 66506; and 4School of Agricultural Biotechnology, Seoul National University, Suwon 441-744 *Corresponding Author: PH: (785)-532-2368; E-mail: [email protected]