Toxicity of deltamethrin pyrethroid on neotropical millipedes, Gymnostreptus olivaceus and Plusioporus setiger

Abstract

The toxicity of Deltamethrin pyrethroid to millipedes Gymnostreptus olivaceus Schubart, 1944 (Spirostreptida, Spirostreptidae) and Plusioporus setiger (Broelemann, 1901) (Spirostreptida, Spirostreptidae), estimated in terms of LD50, was evaluated. The experiments were carried out, using different concentrations of Deltamethrin in form of acetone solutions, applied topically on to dorsal surface of the millipedes. After the applications, millipedes were kept at 25°C during 240 hours, and were observed after 24, 48, 72 & 96 hours. No deaths occurred in the control groups. The LD 50 values estimated (627.0, 154.0, 95.6 and 45.1 1/4g.g-1 for G. olivaceous and 158.2, 67.1, 17.9 and 8.8 1/4g.g-1 for P. setiger) were considered high for both species. The low toxicity of Deltamethrin for these millipedes was attributed to the mode of application topic-way. The adults have a hard and calcified exoskeleton, probably making it difficult the pyrethroid penetration. The ecological aspects and the implications due to improper use of defensives in the environment, are also discussed.