Browsing by Author "Boafo, David"

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    Relative toxicity of three synthetic insecticides and a plant-derived insecticide to oreochromis niloticus and some aquatic invertebrates
    (1991) Boafo, David
    Three synthetic insecticides, Thiodan 35EC, Cymbush 10EC, RoxioN 40EC and a plant-derived insecticide, seed oil were tested against Oreochromis niloticus, Trithemis sp., and Sphaerodema sp. There were no significant differences between the mean weights of the test organisms used for the individual tests (P = 0.05). The temperature of the test solutions for all the test chemicals throughout the test period was in the range of 26°c — 28°C. The pH of the test solutions of Thiodan 35EC and Cymbush 10EC with O. niloticus was 7 throughout the experiments. The dissolved oxygen content of the test solutions ranged from 6.4 mg/l to 7.8 mg/l. The reaction of O. niloticus and the aquatic invertebrates to the various concentrations of the test chemicals was similar; the main symptoms were high excitability, erratic and uncoordinated movements, loss of equilibrium and finally death. The manifestation time generally decreased with increase in the concentration of the test chemicals. The percentage mortality of the test organisms also increased with increase in concentration of the test chemicals. The LC50’s of the synthetic insecticides for the test organisms ranged from 2.66 ppb to 17 782.79 ppb; those of the plant-derived insecticide ranged from 21.13 μl/l to 26.61 μl/l. The LC50’s indicated that O. niloticus is about 4,600 times more susceptible to Thiodan, an organochlorine insecticide, than to Roxion all organophosphate insecticide. Some of the invertebrates, however, were found to the othe tolerant to Thiodan than to Cymbush and Roxion. Sphaerodema sp. was in general more tolerant than the other invertebrates to the synthetic insecticides but more susceptible than the others to the plant-derived insecticide. In general, the order of susceptibility of the various test organisms to the different test chemicals was Thiodan: Berosus sp. > O. niloticus > Sphearrodema sp. > Trithemis sp. Cymbush: Trithemis sp > Berosus sp > Sphearrodema sp. > O. niloticus Roxion: Berosus sp. > Trithemis sp > O. niloticus > Sphearrodema sp J. curcas seed oil: Sphearrodema sp > Berosus sp > Trithemis sp > O. niloticus