Acute toxicity of the insect larvicide abate® (temephos) on the fish tilapia melanopleura and the dragonfly larvae neurocordelia virginiensis.

Abstract

Acute bioassay tests on the toxic effects of the insect larvicide Abate® (temephos) on the mouth brooder cichlid fish Tilapia melanopleum and the dragonfly larvae (Odonata) Neurocordulia virginiensis were conducted in static non renewal toxicity test set ups. The 96h‐LC50 (95% confidence intervals) was 30.2 (20.5‐ 44.20) mg/L for the fish and 2.0 (1.16–2.0) mg/L for the dragonfly larvae. The dragonfly larvae were 15 times more susceptible to the larvicide than the tilapia. The calculated NOEC (No Observable Effect Concentration) was 14.1 mg/L for the fishand less than 1.0 mg/L for the insect larvae. The estimated ‘safe’ concentration of the pesticide to the fish was 3.0 mg/L and 0.2 mg/L for insect larvae. These figures are far above the concentrations approved for use in the control of mosquito larvae(0.0004–0.01 mg/L). It appears that the application of toxic levels of the insecticide for the elimination of some aquatic invertebrates may be ‘safe’ for normal survival, growth and reproduction offish and some aquatic insect larvae.