Feasibility of fumigating unmodified river barges with phosphine while in transit

Six unmodified barges containing corn were fumigated in transit on the Mississippi River between St. Louis, Mo., and New Orleans, La., with aluminum phosphide pellets at the rate of 1.7 g/m3. Insufficient concentrations of phosphine in most areas of the cargo precluded control of either natural pest infestation or caged insects. Also, extensive leaking of phosphine through hatches and lids of barges could lead to hazardous conditions aboard the barge tow or towboat or both. Largest phosphine residue on the grain following fumigation was 0.046 ppm, below established tolerance of 0.1 ppm. Results indicate that fumigation of river barges as presently practiced is ineffective, potentially hazardous, and could lead to development of significant levels of resistance.