DOSE-RESPONSE TESTS ON RED FLOUR BEETLE AND CONFUSED FLOUR BEETLE (COLEOPTERA, TENEBRIONIDAE) COLLECTED FROM FLOUR MILLS IN THE UNITED-STATES

Adults of 14 field strains of the red flour beetle, Tribolium castaneu m (Herbst), and 10 strains of confused flour beetle, Tribolium confusu m Jacqueline DuVal, collected from flour mills were tested for resista nce to malathion and dichlovos by topical application. Lethal dose est imates showed that all strains of T. castaneum were resistant to malat hion and dichlorvos. Some strains showed the highest malathion resista nce ever reported for this insect. Approximately half the strains of T . confusum tested were resistant to malathion and dichlorvos. T. casta neum was more resistant than T. confusum to both malathion and dichlor vos. There was a positive correlation of the lethal dose values for in secticide resistant strains of both species when compared with the sur vival of insects exposed to diagnostic doses. Therefore, survival of i nsects at a diagnostic dose map be used to predict field efficacy of m alathion and dichlorvos in these 2 pest species if resistance levels a re low.