Effect of canopy
structure and wind turbulence on the escape of spores from a soybean
canopy |
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| Predicting the potential arrival of soybean rust through the use of aerobiological models may help growers decide if a fungicide application is needed. Many of the variables that govern aerobiological transport of soybean rust from one location to another are fairly well understood. However, P. pachyrhizi spore escape from a soybean canopy has received little attention. The objective of Jeremy Zidek’s (CEAL MS student) thesis research was to: 1) estimate the proportion of released soybean rust spores that escape a soybean canopy and relate this value to atmospheric turbulence and canopy structure, 2) create concentration profiles of spores and particles and estimate vertical fluxes out of the canopy, and 3) provide a descriptive assessment of the directional and spatial components of movement for spores and particles in and above the canopy. |  |
| Jeremy collected spores for 15-minute intervals near the center of a severely diseased field of soybeans at the University of Florida, North Florida Research and Education Center in Quincy, FL. Spores and spore surrogates (paint chip particles) were also sifted onto healthy canopies and were collected in the same manner. An experiment was also conducted in Pennsylvania using only particles. Rotorod samplers were placed on 4 vertical towers at heights relative to canopy height, h, at the following levels: 0.5h, 1.0h, 1.5h, and 2.5h. The towers were situated in a 3.0 x 3.0 m square. Jeremy measured atmospheric turbulence with a 3-dimensional sonic anemometer (CSAT3). He conducted 37 trials during the 2006 summer. | |
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| Jeremy’s measurements indicate that mechanical atmospheric turbulence, canopy structure, and atmospheric stability are important variables for predicting the proportion of released spores that escape a soybean canopy. The data also indicate that as atmospheric turbulence increases, the vertical escape flux of spores from a soybean canopy also increases. This was especially true for collected spores that were released under ambient environmental conditions. During the PA experiment, Jeremy conducted trials over the course of a season, and the number of particles moving inside the canopy was the most important variable governing the vertical escape flux of particles from a soybean canopy. He attributes this to the change in canopy structure over the course of the season. The measurements also indicated that the strength and direction of the maximum wind gust was an important factor in determining spore transport in and just above the canopy. Zidek, J. M. 2007. Phakopsora pachyrhizi uridiniospore escape from a soybean canopy. Masters Thesis, Pennsylvania State University. |
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