A rainfall simulator was used to evaluate the effects of rainfall intensity and row spacing on Phakopsora pachyrhizi urediniospore wet deposition at different depths within a soybean canopy. Soybean field sections of 19 and 76 cm row spacing were drill planted on two separate dates in Quincy, FL, USA. Urediniospore injected simulated rainfalls of 45 or 85 mm h-1 were conducted within the field sections and urediniospore deposition was quantified in the canopy using a detached leaflet bioassay. The proportion of wet deposited urediniospores retained within the soybean canopy, estimated by uredinia density, was observed to significantly (P < 0.05) decrease with canopy depth. Approximately half of the urediniospores were retained within the upper portion of the soybean canopy, and the other half was distributed between the mid and low canopy sections. Both row spacing and rainfall intensity had no significant (P > 0.10) effect on the vertical distribution of uredinia throughout the soybean canopy, however, more uredinia cm-2 were observed in the upper canopy level for the lower than the higher rainfall intensity. For the treatments examined in this study, it was estimated that between 2.5 and 4.0% of the viable P. pachyrhizi urediniospores that are removed from the atmosphere by rainfall are deposited on and subsequently infect leaves in the mid and low sections of soybean canopies.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science
- Plant Science