November 2004 presentation.


  • Dan Borchert, Glenn Fowler and Roger Magarey (USDA-APHIS-PPQ-CPHST-PERAL)
  • Daryl Jewett (USDA-APHIS)
  • Annalisa Ariatti (UIUC)
  • Scott Isard (PSU)
  • Manuel Colunga and Stewart Gage (MSU)
  • Glenn Hartman and Monte Miles (ARS and NSRL)
  • Thomas Keever and Charlie Main (NCSU)
  • Jeff Grimm, Aaron Hunt and Joe Russo (ZedX, Inc.)


  • The Integrated Aerobiology Modeling System (IAMS) was used to simulate daily soybean rust spore movement (Isard et al., 2004)
  • Viable spore deposition (logarithmic) is modeled from September 15 to 19, 2004 in association with Hurricane Ivan
  • Uncertainty is associated with spore source strength and the absolute quantity of spores

Aerobiological Model Assumptions

  • Source area (17,000 sq Km) was from soybean production areas in northwestern South America
  • Spores were released near midday from August 30 to September 9, 2004
  • 25% of the source area was infested with soybean rust
  • 6 million spores were released per day per heavily infected soybean plant with a planting density of 500,000 plants/ha
  • 33% of these spores were released near midday
  • 15% of the released spores were able to escape from the canopy
  • Mortality due to UVB radiation exposure in the air was proportional to cloud-adjusted surface total incoming solar radiation
  • Wet deposition of viable spores was proportional to the observed surface precipitation total

Computational Procedure

  • Model domain was divided into 14 km2 grid cells
  • NWS reanalysis 2 dataset was used to calculate the most likely downwind direction for 6 pressure levels (altitudes) at 6 hr intervals
  • Spores were moved up or down among pressure levels in accordance to the vertical component of the wind
  • Mortality due to UV exposure and rainout of spores was calculated for each time step after downwind movement
  • Deposition of spores was accumulated for all days in the calculations and is given as the number of spores per hectare

Data Sources

  • Kudzu: Raw data Daryl Jewett (USDA-APHIS) unpublished data. Kudzu map Annalisa Ariatti and Scott Isard (PSU/UIUC).
  • Soybean Acreage: NASS, 2003; National Land Cover Data, 1992; Colunga, 2004
  • Spore Deposition: Isard, S., Main, C., Keever, T., Magarey, R., Redlin, S, and Russo, J. (2004) Weather-Based Assessment of Soybean Rust Threat to North America. Final Report to APHIS
US Planted Soybean Acreage per County
September 15, 2004
September 16, 2004
September 17, 2004
September 18, 2004
September 19, 2004
Planted Soybean Acreage per County
Kudzu Area per County
Soybean Rust Spore Deposition
Soybean Rust Spore Deposition and Planted Soybean Acreage per County
Soybean Rust Spore Deposition and Kudzu Area per County