[Laboratory study on the immediate and persistent insecticide activity of the pyrethroid lambda-cyhalothrin on nymphs of IV instar Triatoma infestans].

Lambda-cyhalothrin (LCT) is a new broad-spectrum synthetic pyrethroid insecticide with efficient immediate and persistent activity against a great variety of arthropods harmful both to human and animal health and to vegetal production. In many countries this insecticide has been successfully used in the control of infectious diseases vectors, such as mosquitoes, triatomine bugs (transmitters of Trypanosoma cruzi, agent of Chagas' disease) and other arthropods. In order to test the immediate and persistent activity of LCT under laboratory conditions (27 degrees C and 75-80% humidity) on laboratory reared Triatoma infestans--the most resistant instar of this insect to the commonest insecticides used--a series of six experiments was performed in 1-year period. Previous to experiments, the interior surface (400 cm2) of 36 specially manufactured cardboard boxes was uniformly sprayed with 2 ml of the following substrates: 12 with 0.6% LCT suspension, 12 with 1.0% LCT suspension and 12 with water (controls). Twenty four hours, 30 - 90 - 150 - 270 and 360 days later, in two pairs of each six boxes, lots of 10 T. infestans IV nymphs were deposited inside of them. In each of the six experiments, daily observations of the conditions of the insects (unaffected, affected in terms of various grades of progressive uncoordination, or dead) after exposure to the insecticide were performed to end with the register of these conditions 96 hours later. Moreover, after 7 and 10 days of exposure in the immediate and persistent effect of LCT respectively a 100% of mortality was verified.(ABSTRACT TRUNCATED AT 250 WORDS)