Sulfluramid resistance and vapor toxicity in field-collected German cockroaches (Dictyoptera: Blattellidae).

The toxicities of Raid Max Roach Bait (sulfluramid) and COMBAT Roach Control System (hydramethylnon) to susceptible and field-collected German cockroaches were examined. In all field-collected strains, a variable fraction of the population exhibited tolerance to Raid Max. In some strains, few males were killed in the first 5 d of exposure to Raid Max and some lived for up to 123 d when provided Raid Max only. Field-collected males that were given access to Raid Max for only 3 h following a 45-h starvation exhibited a 22-fold delay in mortality of 50% of the population compared with males that were continuously exposed to Raid Max. Males exposed to COMBAT for 3 h exhibited a similar pattern of mortality as males continuously exposed to this bait. Field-collected males provided COMBAT with or without rat chow exhibited identical patterns of mortality. However, males that were offered Raid Max along with rat chow exhibited significantly delayed mortality compared with males given Raid Max alone. A direct comparison of 1% hydramethylnon and sulfluramid, the active ingredients in COMBAT and Raid Max, respectively, in rat chow showed that physiological resistance to sulfluramid was involved; field-collected males consumed both baits equally on the first day, but whereas 100% of the males that were fed hydramethylnon-containing chow died within 5 d, only one of 25 males fed sulfluramid-baited rat chow died during this period, and males continued to consume large amounts of food. This suggested that, in the presence of alternate foods, the effective dose of sulfluramid was diminished, resulting in reduced mortality in males fed Raid Max. These results suggest that relatively high levels of resistance to sulfluramid are pervasive in field populations of the German cockroach. Experiments in which cockroaches were exposed to vapors of Raid Max or sulfluramid without direct contact showed that both acted as fumigants. The Raid Max bait remained lethal without direct contact for at least 170 d of continuous aeration in a fume hood. A headspace analysis revealed that sulfluramid was present in airborne collections of both technical sulfluramid and the Raid Max bait.