Evaluation of Closed Loop Fumigation in Large Steel Unsealed Silos in Western Australia
Many large bolted silos with a capacity greater than 500 m are constructed unsealed in Australia unless full sealing is specified by the client. These silos may have a sealing compound inserted between each wall sheet and the base concrete but have open eaves, no sealing between the roof lap joints and unsealed access ports. The fumigant phosphine is used routinely to control stored grain insects in this type of silo. The efficacy of these fumigations is questionable and gas may be lost before all life stages of the insect are controlled and with the potential to select for phosphine resistance. To control all life stages of the target species the gas must be retained within the grain for the period specified in the protocol. To achieve full control of insects in these silos sealing is recommended but it is a more complicated and costly procedure to seal after construction. The addition of a recirculation（Closed Loop)system in conjunction with additional joint sealing and sealing of access ports may enhance distribution of gas throughout the grain profile. This paper reports on an investigation into fumigations in bolted steel silos ranging from 835 m to 1 729m3, ambient weather effects on the gas values and the impact of direction of airflow within the silo. Fumigation results varied according to the ambient conditions and the air flow direction created by the recirculation fan. A protocol of 100 ppm for seven days for susceptible grain beetles was reached in some storage under low ambient wind conditions but failed to reach this protocol under high wind conditions. Fumigant loss was high when the gas was blown into the headspace and there was improved retention when the gas was extracted from the headspace and blown into the base.
closed loop fumigation phosphine
Christopher R.Newman
Department of Agriculture and Food Western Australia, Bougainvillea Ave., Forrestfield, WA, 6058, Australia
国际会议
成都
英文
241-245
2008-09-21（万方平台首次上网日期，不代表论文的发表时间）