Comparative toxicity of deltamethrin and cis-permethrin on first instars of Triatoma infestans (Hemiptera: Reduviidae).

We evaluated the toxicity of deltamethrin and cis-permethrin at 3 temperatures on instars of Triatoma infestans (Klug). After treatment, temperature had an important effect on LD50s of both insecticides, which tended to decrease when temperature decreased. However, the effect of temperature on LT50s was small. Cis-permethrin was slightly more lethal than deltamethrin only at 26 degrees C. Lethal action of deltamethrin was faster than cis-permethrin at all temperatures assayed. The toxicity of both pyrethroids was affected by the age and the nutritional state of the nymphs. We evaluated sublethal effects on blood meal ingestion and moulting. Only deltamethrin yielded a substantial decrease in the number of moulted nymphs.