Field evaluation of grain protectants in stored maize in the Philippines
1998
Sayaboc, P.D. | Acda, M.A. | Cano, F.A. Jr. | Gibe, A.J.G. | Gragasin, M.C.B.
A field trial was carried out in General Santos City and Cebu City [Philippines] to validate the efficacy of candidate grain protectant treatments as follows: 1.) chlorpyrifos-methyl (10 mg/kg) plus permethrin (1 mg/kg) plus piperonyl butoxide (10 mg/kg); 2.) deltamethrin (1 mg/kg); 3.) fenitrothion (12 mg/kg) plus fenvalerate (1 mg/kg) plus piperonyl butoxide (10 mg/kg); 4.) methacrifos (20 mg/kg); and 5.) pirimiphos-methyl (6 mg/kg) plus carbaryl (8 mg/kg). Following treatment at Gen. Santos City, the grain was bagged, shipped by sea to Cebu City and kept in a commercial store for 9 months. Significant losses of insecticides incurred during application ranged from 22 percent to 80 percent of the calculated application rates. Consequently, mean residues after 9 months ranged from 1 percent to 10 percent of the calculated application rates, except for fenvalerate (20 percent). Laboratory bioassays on samples of treated grain at intervals over 9 months of storage using strains of Rhizopertha dominica (F.), Sitophilus zeamais Motschulsky, Tribolium castaneum (Herbst) and Trogoderma granarium Everts confimed that treatments were generally more effective than the industry practice. Significantly, the suppression of the highly destructive T. granarium was complete for all admixture treatments throughout the storage period. Deltamethrin was not fully effective against Sitophilus zeamais and methacrifos was fully effective against Rhizopertha dominica only in the initial assay. Workers experienced dermal and respiratory irritation with exposure to deltamethrin F and an alternative formulation would be required for use in grain storage
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