Evaluation of wireless phosphine sensors for monitoring fumigation gas in wheat stored in farm-bins

Authors: Brabec, Daniel - Dan; Campbell, James - Jim; Arthur, Franklin; Casada, Mark; Tilley, Dennis

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2019
Publication Date: 4/27/2019
Citation: Brabec, D.L., Campbell, J.F., Arthur, F.H., Casada, M.E., Tilley, D.R. 2019. Evaluation of wireless phosphine sensors for monitoring fumigation gas in wheat stored in farm-bins. Insects. 10(5):121. https://doi.org/10.3390/insects10050121.
DOI: https://doi.org/10.3390/insects10050121

Interpretive Summary: Fumigation of grain bins and storage containers with phosphine is one method of dis-infesting stored products. Monitoring the concentration of the toxic gas at many locations over several days for a given structure or container is difficult. Manually monitoring the concentration over many days is time consuming for employees and limited due to employee availability, especially during the night. A commercially-available system was evaluated that included phosphine sensors, wireless communications, and internet data collection software. The wireless devices collected local phosphine concentrations and temperatures every two hours without assistance from personnel. The automated data provided a more detailed picture of the phosphine concentrations and changes. Fumigation managers would be able to more safely collect and view the fumigations easily on internet connected devices and better evaluate fumigations for proper toxic gas concentrations and holding periods necessary for effectively controlling insect infestations.

Technical Abstract: Fumigation of grain bins with phosphine tablets is one method of insect control in stored products. The phosphine tablets react with moist air and produce a toxic gas environment that needs to be contained in the grain bin for several days for effective insect control. Monitoring the concentration of the toxic gas at many locations over several days for a given structure or container is difficult, because grain bins or other structures can be difficult to access. Also, manually monitoring the concentration over many days is time consuming for employees and limited due to employee availability, especially during the night. A commercially-available system was evaluated that included four phosphine sensors, wireless communications, and data collection software. This system was evaluated in two ways; small-scale and large-scale tests. Small scale testing was performed to study the repeatability and accuracy of a group of four sensors. All four sensors were placed into a single container, a 208-liter barrel, and a phosphine pellet was added. The remote sensors were within 30 ppm of each other over a range of 700 ppm phosphine. The wireless sensors were within 7% of the airline sampling data in 15 of 17 observations. Large scale testing evaluated the system during the fumigation of wheat stored in 120 metric ton, steel grain bins. Two 7m-diameter grain bins were used and two phosphine sensors were added to the top of each bin. As a reference, airlines were distributed at several positions and depths in the bin for sampling the phosphine gas concentrations using a phosphine meter. A series of three fumigation trials were done with each lasting over 6 days. The wireless devices collected local phosphine concentrations and temperatures every 2 hours without assistance from personnel. During the day, airlines were sampled every 6-8 hours but no samples were taken at night. Fumigation trials were significantly different. The air sampling data and the phosphine sensors data gave similar trendlines. However, the automated data provided a more detailed picture of the phosphine concentrations and changes. The wireless sensor has the limitation of monitoring a specific location in the gas mass and multiple sensors would give better information regarding distribution of the gas at both high and low levels of the grain mass. With this type of monitoring system, fumigation managers would be able to more safely collect and, with the increased data values, better evaluate fumigations. Sub-cycle events were evident with the phosphine data such as fans turning off and on, which changed concentration levels. In addition, the phosphine concentration data was easily collected and available on viewing on the office computer using the wireless sensors. Future research efforts will examine phosphine monitoring with the sensors in railcars.