Wet and Dry Deposition
of Soybean Rust Urediniospores |
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| The spores of many plant pathogens can
be transported vast distances through the atmosphere to susceptible
host populations. These airborne spores can be deposited by sedimentation
and impaction (dry deposition) and/or by rainfall (wet deposition).
Past research has examined the deposition processes of spores and
particles into a number of plant canopies but deposition processes
have not been studied in soybean. The spores of the devastating pathogen
Phakopsora pachyrhizi are aerial dispersed to their soybean
hosts. |
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 Particles released through a standard sieve with a vibrating motor |
| Nick conducted a number of preliminary studies to determine how artificial plants and particles could be used to study dry deposition process in soybean canopies (Dufault et al 2006a). He found that comparable amounts of particles were dry deposited into the upper and mid portions of the soybean canopy for both 7 and 30 inch row spacing treatments. Dry deposition into the mid canopy at low wind speeds decreases as the canopy matures and more leaf area becomes present. This indicates that spores similar in size and density to the particles will be distributed evenly throughout both canopy treatments. Nick is now conducting further dry deposition research with both particles and P. pachyrhizi urediniospores. Preliminary results suggest that the spores behave similarly to the particles under the same treatment conditions. | |
 Rain simulator |
Nick has also modified a portable rainfall simulator, previously used for rain runoff research to study wet deposition of P. pachyrhizi urediniospores (Dufault et al 2006b). He has been able to calibrate the simulator and confirm that comparable amounts of viable spores can be deposited onto soybean plants within each quadrant of the rain simulators sampling area. The results from preliminary field studies with plants in 36 inch row spacing, showed that there was no significant difference in the vertical distribution of pustules produced from spores in the simulator rainfall at two application rates. The simulator produces droplets similar in size and velocity to those observed in natural rainfall. Thus preliminary results suggest that this rain simulator can be used effectively to investigate the vertical distribution of wet deposited spores into soybean canopies. |