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12

A portable rainfall simulator for conducting wet deposition field measurements of Phakopsora pachyrhizi urediniospores

Presenter: N. S. Dufault

All authors and affiliations: N. S. DUFAULT (1), S. A. Isard (1), E. D. DeWolf (1), D. Wright (2), and J. Marois (2). (1) Department of Plant Pathology, The Pennsylvania State University, University Park, PA; and (2) North Florida Research and Education Center, University of Florida, Quincy, FL

The wet deposition of Phakopsora pachyrhizi urediniospores by rainfall is an important process in the transportation of the fungus vast distances. In the past, stationary rainfall simulators have been used to examine the wet deposition and dispersal of plant pathogens in vitro. However, the use of rainfall simulators in plant disease field studies has not been extensively documented. This work describes how a rainfall simulator used in phosphorus runoff studies was adapted for wet deposition experiments with P. pachyrhizi urediniospores. The frame of the simulator was constructed of 3.18-cm (1.25 in)-diameter aluminum pipes, and when assembled, it creates a sampling area the size of 2 × 2 m. A single Fulljet nozzle (24 or 30 WSQ) was centered on an adjustable arm approximately 3 m above the simulator’s base. Urediniospore wet deposition was simulated by injecting pressurized spore solutions directly into the water flow. The operating flow rates were maintained at 1.8 and 2.2 gallons per minute with plot coefficient of uniformities of 85 and 75% for the 24 and 30 WSQ nozzles, respectively. The median droplet size for the 24 WSQ was 0.75 mm, and 1.25 mm for the 30 WSQ. Leaf bioassays from rain simulations in both controlled and field environments confirmed that viable spores were deposited onto soybean leaves. This rain simulator will be used to investigate the vertical distribution of wet-deposited spores into a soybean canopy at different rain intensities and row spacings.

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