Toxicity of methyl bromide and other gaseous insecticides to Triatoma infestans

Cuticular penetration of lipid soluble substances in Triatoma infestans is very poor (less than 1% in 24 hr), while the respiratory route is particularly efficient (28% in 5 min). Accordingly, several noxious gases killed the insect at short periods of time. CH3Br and SO2 were particularly effective and they also evidenced ovicide action. With the former compound this effect is also observed at low concentrations. The CH3Br hydrolysis products or its metabolites were not similarly effective, while other methylating agent, diazomethane, was very active. The irreversible binding of 14CH3Br to proteins and lipids of T. infestans, as well as the decrease in the sulfhydryl groups content of the proteins of the insect provoked by CH3Br suggest that this compound kills the insect because of its alkylating properties. The use of gaseous insecticides in the chemical control of T. infestans is discussed.