Phosphine distribution patterns during fumigation of binned wheat

Authors: Pordesimo, Lester; Casada, Mark; PETINGCO, MARVIN - Kansas State University; SILIVERU, KALIRAMESH - Kansas State University

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2025
Publication Date: 12/17/2025
Citation: Pordesimo, L.O., Casada, M.E., Petingco, M.C., Siliveru, K. 2025. Phosphine distribution patterns during fumigation of binned wheat. Applied Engineering in Agriculture. https://doi.org/10.13031/aea.16200.
DOI: https://doi.org/10.13031/aea.16200

Interpretive Summary: Phosphine fumigation is widely used to control stored product insects in grain storage bins; however, the effectiveness of this practice is often compromised by non-uniform distribution of the gas resulting in areas of the bin that do not receive sufficient gas to cause insect mortality. The non-uniformity in fumigant gas distribution can be caused by several factor such as leaks in the grain bin structure and the method of applying the phosphine. The purpose of this study was to measure the concentration and distribution of phosphine gas in grain bins containing hard red winter wheat using three different application methods (inserting phosphine tablets into the grain mass (conventional method), inserting phosphine tablets and covering grain surface with a tarp (reduce phosphine loss from the grain surface), and applying phosphine tablets to the surface of grain and using a fan to circulate the gas through the bin (closed loop fumigation (CLF)) to determine which method reaches the most optimal concentration of gas throughout the bin (defined as >200 parts per million (ppm)). Contour plots of phosphine movement showed leakage and uneven distribution patterns over time with conventional probed tablets, which resulted in some areas in the lower half of the grain mass receiving a zero dose and some other locations remaining below the target phosphine concentration of 200 ppm for the entire period of fumigation. With CLF, phosphine concentrations were uniform throughout the bin levels at each time step but measured average phosphine concentrations levels were lower than those measured with conventional fumigations. This observation indicates that in this study leakage was higher in CLF compared to conventional fumigations, which is likely due to the recirculation fan pressure. CLF delivers on its potential to produce more uniform fumigant distribution and would be expected to produce effective concentration levels when it is implemented in a well-sealed structure. Future work will determine if better sealing in combination with air circulation with a fan will result in a more effective fumigation.

Technical Abstract: Effectiveness of fumigation with phosphine is often compromised by suboptimal distribution of the gas. The non-uniformity in fumigant gas distribution can be caused by several factor such as leaks in the grain bin structure, foreign material in the grain, and placement of the phosphine source material. Many workers in fumigation have stressed that the most important factor is the ability of the grain storage structure to retain the fumigant gas. Phosphine concentration and distribution was studied during field tests with two replications in U.S. corrugated steel bins containing 95 t of hard red winter wheat. The bins were sealed following bin sealing recommendation, except the eave to sidewall seal had become aged, and phosphine was applied by conventional probe-only and probe and tarp techniques and by closed loop fumigation (CLF). Contour plots of phosphine movement showed leakage and uneven distribution patterns over time with conventional probed tablets, which resulted in some areas in the lower half of the grain mass receiving a zero dose and some other locations remaining below the target phosphine concentration of 200 ppm for the entire period of fumigation. With closed loop fumigation, phosphine concentrations were uniform throughout the bin levels at each time step but measured average phosphine concentrations levels were lower than those measured with conventional fumigations, indicating that leakage was higher from the same bins used in conventional fumigations that is likely due to the recirculation fan pressure. CLF delivers on its potential to produce more uniform fumigant distribution and would be expected to produce effective concentration levels when it is implemented in a well-sealed structure.