Toxicity of Diflubenzuron on Juveniles of African Brackish Water Shrimp from Lagoon Coastline and Mosquito Larvae from Breeding Places in a Tertiary Institution in Lagos, Nigeria

Abstract

Diflubenzuron (DFB) prevents chitin formation and cuticle deposition in insects. Its application can inadvertently enter into aquatic ecosystems, with potential adverse impacts on selected aquatic biota. Hence, the objective of this study was to evaluate the toxicity of diflubenzuron on juveniles of African brackish water shrimp from the Lagoon Coastline and mosquito larvae from breeding places in a tertiary institution in Lagos, Nigeria using appropriate standard techniques. The result of the lethal toxicity showed that LC₅₀ toxicity factor of DFB on Aedes and Culex larvae were significantly higher (p < 0.05) for 24hrs compared to other time intervals. Exposure of the African brackish water shrimp to diflubenzuron had LC₅, LC₅₀, and LC₉₅ values of 0.115 mg/L, 8.510 mg/L, and 627.048 mg/L, respectively at 24hrs. Adult emergence inhibition of DFB on Aedes and Culex larvae showed highest adult emergence inhibition (≥ 90%) at 0.0001 mg/l after 12 days, while similar inhibition was achieved after 8 days for 0.005 mg/l. Diflubenzuron residue in water decreased with exposure time while that detected in P. africanus increased to a maximum of 42.13±3.7 ug/g and 301.03±13.7 ug/g for 100 ug/l and 1000 ug/l respectively after 14 days. The findings demonstrated that DFB is relatively stable in water, and its benign toxicity to non-target organisms makes it ideal for mosquito larval control.