author(s)
Innocent E, Kisanga AC, Gamba N, Kisinza WN and Hassanali A

abstract
Plant extracts from the genus Annona exhibit insecticidal properties and thus, may offer an alternative to synthetic insecticides. In the present study larvicidal efficacy of formulations of Annona squamosa and A. montana were evaluated against Anopheline and Culicine larvae in the laboratory and semi-field conditions. In the laboratory there was no significant difference (t=0.5313, p>0.05) in the effectiveness of the A. squamosa formulation at 50 µg/ml and above between An. gambiae and Culex quinquefasciatus by day 4. Significant difference (t= 2.649, p<0.05) was observed for A. montana formulation at higher concentration than 50 µg/ml since An. gambiae was more susceptible than Cx. quinquefasciatus. In semi-field condition the efficacy of the two formulations against Anopheline was not quite significant (t= 2.504, p>0.05). The activity of A. montana leaf powder against Culicines was significantly lower compared to A. squamosa (t=3.827, P<0.05). The variation in water parameters had no significant effect on the efficacy of the formulations. The formulations did not affect the survival of the 9 invertebrate groups tested during the period of study except for the Order Ephemeroptera (Mayflies) whose mortalities was more than 85%. The formulations have proven to offer an alternative to synthetic insecticides.