Phosphine resistance in cigarette beetle (Coleoptera: Anobiidae) associated with tobacco storage in the Southeastern United States

Twenty field strains of cigarette beetle, Lasioderma serricorne (F.), were collected from tobacco storages in the southeastern United States from July 1990 through October 1991. These strains were reared in the laboratory and F sub(1) adults were tested for phosphine resistance by exposing adults to a diagnostic dose of 25 ppm for 24 h in 2.5-liter desiccator jars. Based on the percentage of survivors of the treatment as an estimate of the frequency of resistance in the population, results showed that 11 strains were resistant with survivals ranging from 2 to 97%. Nine susceptible strains showed no survival. Two resistant strains, tested with multiples of the diagnostic dose, showed survival of 12 and 24% at 125 ppm; their resistance ratios were five-fold compared with the phosphine susceptible strain. No control failures have been attributed yet to phosphine resistance in the cigarette beetle. However, the frequency and intensity of the resistance suggest that normal fumigation techniques will become increasingly less effective.