Toxicidad de cinco insecticidas en una cepa de laboratorio de Rhodnius prolixus Stål, 1859 (Hemiptera: Reduviidae) de Venezuela

Soto Vivas A, Molina de Fernández D. 2001. Toxicity of five insecticides in a laboratory strain of Rhodnius prolixus Stål, 1859 (Hemiptera: Reduviidae) from Venezuela. Entomotropica 16(3):187-190. The baseline of susceptibility to insecticides was determined in nymphs of first and fifth instar from Chagas strain of Rhodnius prolixus maintained in laboratory for about 30 years without contribution of external material and without exposure to insecticides. In bioassays, 24 hours old nymphs of first instar, starved since eclosion (mean weight of 0.6±0.1 mg ) were used, as well as 12-13 days old fifth instar nymphs, (mean weight 142±10 mg). The LD50 values were determinted by topical application bioassays and were expressed in nanograms by insect. The first instar nymphs exhibited LD50 values of 2.4 ng/i to fenitrothion, 13 ng/i to pirimiphos methyl, 13 ng/i to propoxur, 1.4x10-3 ng/i to lambdacyhalothrin and 1x10-4 to deltamethrin, and the fifth instar nymphs exhibited LD50 values of 100 ng/i to fenitrothion, 700 ng/i to pirimiphos methyl, 690 ng/i to propoxur, 6.6 ng/i to lambdacyhalothrin and 18 ng/i. to deltamethrin. The R. prolixus "Chagas" strain studied in the present work showed heterogeneity in its response to pyretroid insecticides