Phosphine concentration fluctuations in freight railcars during “in transit” fumigations

Authors: Brabec, Daniel; ATHANASSIOU, CHRISTOS - Kansas State University; CAMPBELL, JAMES - Retired ARS Employee; ARTHUR, FRANK - Retired ARS Employee

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2026
Publication Date: 6/25/2026
Citation: Brabec, D.L., Athanassiou, C., Campbell, J., Arthur, F. 2026. Phosphine concentration fluctuations in freight railcars during “in transit” fumigations. Journal of Stored Products Research. https://doi.org/10.1016/j.jspr.2026.103124.
DOI: https://doi.org/10.1016/j.jspr.2026.103124

Interpretive Summary: Railcars transport approximately 25% of US grain, often undergoing "in-transit" phosphine fumigation to manage and insect infestations. Historically, monitoring these moving treatments was unfeasible. However, this study utilizes recent advancements in wireless phosphine and temperature sensors to evaluate fumigation efficacy during transport. Twenty-four fumigation trials were conducted over four seasons (2018–2023) across two grain processing facilities. Monitoring focused on freight railcars during transit, evaluating phosphine concentrations and the impact of ambient temperature fluctuations. Early trials (2018) at Location A showed poor results, with 75% of railcars recording weak fumigations, which would have been unsuccessful in controlling insect infestations. However, by 2019 and 2023, Location A improved to a 66% strong success rate, largely due to enhanced sealing practices, such as taping plastic sheeting over side doors. Conversely, Location B struggled in 2021, with 50% of trials resulting in weak fumigation. Data indicates that while air temperature fluctuations directly influence gas concentrations, physical sealing remains the primary driver of success. Overall, our study shows that wireless sensor technology is essential for verifying fumigation effectiveness and optimizing sealing protocols to protect grain quality during transit and throughout the entire post-harvest supply chain.

Technical Abstract: Technologies to monitor moving railcar fumigations have become available in the last decade. These technologies were deployed to help the grain industry understand current railcar fumigation performances and consider improved practices. Phosphine concentrations and temperature fluctuations were monitored during 24 separate railcar fumigation events that were carried out in moving freight railcars during 2018, 2019, 2021, and 2023 at two locations using portable gas sensing devices. The efficacies of the fumigation were predicted by calculating a Concentration*Time (Conc*T) to summarize each trial which were classified as strong (Conc*T >25,000 ppm*hr), mid (15,000 to 25,000 ppm*hr), or weak (< 15,000 ppm*hr), which were based on prior fumigation studies using adult phosphine resistant insects. We achieved mid or strong fumigations in about 63% of the railcars tested, yet 37% of the railcars were weak and were predicted to result in low control of phosphine resistant strains. The lower Conc*T values could have resulted from leaky railcars or poor railcar sealing practices. We tested fumigation efficacies at two different facilities (A and B). Facility B was used one year and tended to have weak fumigations. Facility A was used in three years. Although, fumigation efficacies at A started weak, they improved over time because the staff took additional steps to seal the railcars better, such as tarping the doors to reduce leakage. Temperature data was collected during all fumigations monitoring events and it was correlated to changes in phosphine concentration. Daily changes in temperature had a secondary effect on the phosphine concentration and could have resulted in sublethal doses of phosphine at various times during the transit fumigations. Overall, our study shows that real-time fumigation monitoring is a valuable tool to determine the actual fumigation effectiveness during transit, which can reduce post-harvest losses during transit.