PHOSPHINE RESISTANCE IN CIGARETTE BEETLE (COLEOPTERA, ANOBIIDAE) ASSOCIATED WITH TOBACCO STORAGE IN THE SOUTHEASTERN UNITED-STATES

Twenty field strains of cigarette beetle, Lasioderma serricorne (F1), were collected from tobacco storages in the southeastern United States from July 1990 through October 1991. These strains were reared in the laboratory and F1 adults were tested for phosphine resistance by expo sing adults to a diagnostic dose of 25 ppm for 24 h in 2.5-liter desic cator jars. Based on the percentage of survivors of the treatment as a n estimate of the frequency of resistance in that population, results showed that 11 strains were resistant with survivals ranging from 2 to 97%. Nine susceptible strains showed no survival. Two resistant strai ns, tested with multiples of the diagnostic dose, showed survival of 1 2 and 24% at 125 ppm; their resistance ratios were five-fold compared with the phosphine susceptible strain. No control failures have been a ttributed yet to phosphine resistance in the cigarette beetle. However , the frequency and intensity of the resistance suggest that normal fu migation techniques will become increasingly less effective.