Efficiency of certain insecticides against Bruchidius incarnatus [Schm.] and determination of their residues in broad bean plants and soil

ABSTRACT

The efficiency of profenofos, chlorpyriphos, chlorpyriphos - methyl and Malathion insecticides against the egg stage [taken as indicated effect of adults] of bean bruchids Bruchidius incarnates [Schm.] beetles infesting broad bean pods in the field was studied. Percent reduction in infestation was 93.6, 91.1, 95.0 and 89.1% in treated plants by pervious insecticides, respectively after one day of application. After fifteen days from spraying, the percent reduction infestation was, 62.0, 61.7, 51.6 and 30.1%, respectively. The residual behavior of these insecticides on and in green broad pods and their seeds was studied and persistence of these chemicals in the planted soil was also determined. The results indicated that the initial deposits determined on and in green pods one hour following application were 16.32, 12.67, 14.16 and 17.16 ppm for profenofos, chlorpyriphos, chlorpyriphos methyl and Malathion, respectively. The corresponding amounts in soil were 2.07, 1.22, 1.67 and 2.16 ppm. The percentages of loss of residues in pods were 38.05, 30.7, 37.07 and 38.17% one day after treatment, respectively. The preharvest intervals were 5 and 15 days for treated green pods by Malathion and/or chlorpyriphos-methyl, while this period is more than fifteen days in case of profenofos and chlorpyriphos. Green seeds could be safely used at any time after spraying because peeling the green pods removed most of the tested insecticide residues