RESIDUAL EFFECT OF LAMBDACYHALOTHRIN ON TRIATOMA-INFESTANS

Insecticidal residual effect and triatomine infestation rates in house s of a community fumigated with lambdcyhalothrin (Icon) are reported. No mortality was observed in 5th-instar Triatoma infestans nymphs in 7 2-hr exposure test on three different surfaces, one month after fumiga tion for a dose of 31.5 mg am/m(2). However, during post-exposure obse rvation a mortality of 60% was recorded for those insect exposed on sp rayed woodboard. The results observed with mud-containing treated wall s, were markedly poorer (0% of mortality). Twelve month after spraying 40% of mortality was observed on first-instar T. infestans nymphs in 72-hr exposure test on woodboard, but lower mortality rates were obser ved in mud-containing materials. When the effect of deltamethrin (109 mg ai/m(2)) and lambdacyhalothrin (94 mg ai/m(2)) was compared, the fo rmer did not appear to be superior at similar loads. Both have showed a mortality rate of 30% on 5th-instar T. infestans nymphs three months post-fumigation. The dose utilized in the field fumigation was enough to get a significant (p < 0.001) control of triatomine domestic infes tation, since it was sufficient to keep 95% of the houses uninfested t hroughout 21 months following treatment, when compared with baseline s ituation. A remarkable knock-down effect on adult and nymphs forms of the insect and a high in situ mortality were observed as a result of i ts application, even at very low doses.