Larvicidal activity of six Nigerian plant species against Anopheles gambiae and Aedes aegypti
Nigeria has diverse natural vegetation and some indigenous plant species have been reported to have insecticidal activities. This study evaluated the larvicidal activity of extracts from six Nigerian plant species (Zanthoxylum zanthoxyloides, Piper guineense, Nicotianat abacum, Erythrophleum suaveoleus, Jatropha curcas and Petiveria alliacea) against laboratory-bred Anopheles gambiae and Aedes aegypti larvae. Zanthoxylum zanthoxyloides extract was the most toxic against An. Gambiae larvae with 24h LC50 value of 0.985 g/L. This was followed by P. guineense with 24h LC50 value of 2.185 g/L and N. tabacum, 3.786 g/L while P. alliacea was the least toxic with 24h LC50 value of 22.613 g/L. Zanthoxylum zanthoxyloides extract was also the most toxic for Ae. aegypti larvae with 24h LC50 value of 2.084 g/L. This was followed by P. guineense, 4.378 g/L and N. tabacum, 15.059 g/L while P. alliacea was also the least toxic. Actellic, which was used as the standard synthetic larvicide in this study, was significantly (p<0.05) more potent on the test larvae than all the plant extracts at the concentration used, though its toxicity was comparable to that of Z. zanthoxyloides extracts which suggests that with further purification, this plant extract might compete better with synthetic insecticides. Locally available plant species with insecticidal activities have potential to complement existing malaria control measures and may constitute potential candidates for new sources of larvicides that could be incorporated into the National Malaria Elimination Programme.
Keywords: Plant extract; larvicidal; Anopheles gambiae larvae; Aedes aegypti larvae