Este trabalho trata do estudo da toxicidade de contato do dichlorvos, chlorpyrifos-methyl, malathion e lindane para larvas de Plodia interpunctella (Hübner, 1813) (Lepidoptera, Pyralidae); e da avaliação da eficiência de proteção dada pelo pirimiphos-methyl, chlorpyrifos-methyl, malathion e dichlorvos para sementes de milho contra essa praga. Os experimentos foram conduzidos no Departamento de Entomologia da Escola Superior de Agricultura “Luiz de Queiroz”, da Universidade de São Paulo. A temperatura e umidade relativa foram 28 ± 2°C e 70 ± 10%. A toxicidade dos inseticidas foi avaliada através dos valores DL_{5 0} e DL_{9 5} e o malathion foi usado como padrão para a comparação. O dichlorvos foi o inseticida mais tóxico para larvas de P. interpunctella. O chlorpyrifos-methyl mostrou maior toxicidade que o malathion. O lindane foi o menos tóxico para larvas machos. O malathion foi o menos tóxico para larvas fêmeas. Todos os inseticidas foram mais tóxicos para as larvas machos que para larvas fêmeas. As larvas machos foram mais tolerantes ao chlorpyrifos-methyl e dichlorvos que as larvas fêmeas. As larvas fêmeas foram mais tolerantes ao malathion e lindane que as larvas machos. Pirimiphos-methyl (15 e 10 ppm), chlorpyrifos-methyl (30 ppm) e malathion (30 ppm) foram eficientes no controle de adultos durante 5 meses de armazenamento. Chlorpyriphos-methyl (20 ppm) e malathion (20 e 10 ppm) foram eficientes no controle de adultos durante três meses de armazenamento. Dichlorvos (45, 30 e 15 ppm) e pirimiphos-methyl (5 ppm) foram eficientes no controle de adultos durante um mês de armazenamento.

This paper deals with the study of the direct-contact toxicity of dichlorvos, chlorpyrifos-methyl, malathion and lindane to Plodia interpunctella larvae (Hübner, 1813) (Lepidoptera, Pyralidae); and the evaluation of the efficiency of protection given by pirimiphos-methyl, chlorpyrifos-methyl, malathion and dichlorvos to seed corn against P. interpunctella. The experiments were carried out at the Department of Entomology of Escola Superior de Agricultura “Luiz de Queiroz”, University of São Paulo, in Piracicaba, State of São Paulo, Brazil. Temperature and relative humidity were 28 ± 2°C and 70 ± 10%. The toxicity of the insecticides was evaluated by LD_{5 0} and LD_{9 5} values and malathion was used as a standard for comparison. Dichlorvos was the most toxic insecticide to P. interpunctella larvae. Chlorpyrifos-methyl showed greater toxicity than malathion. Lindane was the less toxic to male larvae. Malathion was the less toxic to female larvae. All insecticides were more toxic to male larvae than to female larvae. Male larvae were more tolerant to chlorpyrifos-methyl and dichlorvos than female larvae. Female larvae were more tolerant to malathion and lindane than male larvae. Pirimiphos-methyl (15 and 10 ppm), chlorpyrifos-methyl (30 ppm) and malathion (30 ppm) were efficient for adult control for five months storage. Chlorpyrifos-methyl (20 ppm) and malathion (20 and 10 ppm) were efficient for adult control for three months storage. Dichlorvos (45, 30 arid 15 ppm) and pirimiphos-methyl (5 ppm) were efficient for adult control for one month storage.