AN APPROACH FOR DEVELOPING A PHOSPHINE DOSAGE PROCEDURE AND CALCULATOR FOR SILO BAGS

RICARDO BARTOSIK; LEANDRO CARDOSO; DIEGO DE LA TORRE; MARÍA BERNADETTE ABADIA; MARTIN IGARTUA

Nueva Delhi

Conferencia; 10th International Conference on Controlled Atmospheres and Fumigations; 2016

CAF Permanent Committee

PH3 is the main fumigant and one of the most used chemical insecticides worldwide for stored product pests. For achieving an effective pest control with PH3, a minimum concentration has to be maintained during a minimum exposure time (ct-product, e.g. 200 ppm during 120 h). However, PH3 concentration evolution in time is difficult to predict since it depends on the initial fumigant dose, the fumigant losses during the treatment, and the fumigant sorption by the product, among others. Although critical information for a successful fumigation is available, this information is not clearly integrated or easily available for farmers and grain elevators managers for practical fumigation recommendations. Thus, the aim of this study was to integrate the available information and develop a PH3 dosage procedure and calculator for silo bags. An automatic pressure decay test (APDT) device was developed, consisting on a portable plastic suitcase, including an electrical fan, connecting hoses, pressure gauge, valves and a controller. The controller has Bluetooth connectivity so all the parameters recorded by the APDT are automatically transmitted to the cell phone. Based on literature data, correlations were developed to estimate PH3 losses according to PDT results in silo bags. A PH3 concentration prediction model that takes into account PH3 liberation from aluminum phosphide, PH3 losses, void spaces and PH3 sorption by the grain was proposed and compared with experimental results. It was observed that losses were overestimated when the silo bag had a PDT close to 60 seconds and an enhanced model was proposed and validated with literature data. The need of better correlations for estimating PH3 losses in silo bags and PH3 release were discussed. A procedure for calculating the dosage for a successful PH3 fumigation was proposed, which combines the use of the APDT device and the PH3 concentration model (programmed in Excel).