Phosphine concentration change during fumigation in hermetic plastic bags (Silobags)

Authors: Cardoso, L., Bartosik, R., Milanesio, M.

INTA, EEA Balcarce – Ruta 226 km 73,5 (7620) Balcarce, Buenos
Aires, Argentina.
Facultad de Ciencias Agrarias Balcarce, Ruta 226 km 73,5 (7620) Balcarce, Buenos Aires, Argentina.

Abstract: The goal of this experiment was to develop and test a suitable methodology for treatment of grain stored in plastic bags with phosphine. The treatment should guarantee a 200 ppm concentration of phosphine during at least 5 days. Two plastic bags storing about 200 tonnes of dry wheat each were used for the test, and a third bag was used as control. The first treatment consisted of adding 1 tablet of aluminum phosphide per cubic meter (3 g/m3 of aluminum phosphide or 1 g/m3 of phosphine) and the second treatment duplicated the dosage. The tablets were inserted each 5 linear meters along the bag. Additionally, cages containing live insects
(Sitophilus oryzae) were inserted in different locations of the bag. Phosphine concentration was daily measured in different locations of the bag during 10 days. After the treatment, the cages with insects were inspected and insect mortality was recorded. The main results indicated that the treatment with the lowest phosphine concentration (1 g/m3) was enough to reach the target concentration during 5 days in most of the bag. The area close to the end of the bag resulted with lower than desired phosphine concentration, indicating lack of airtightness in that sector. The
areas closer to the location where the aluminum phosphide tablets were inserted resulted with higher phosphine concentrations than other areas. However, spacing the application points each 5 m along the bag resulted in an efficient gas distribution. Insect mortality was 100% in both treatments, while in the control mortality was between 13 and 33%.

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