Evaluation of Water Extracts from Seven Sudanese Plants as Natural Insecticides

Laboratory studies were carried out to evaluate the insecticidal potentialities of water extracts prepared from seven indigenous plant species in Sudan. These plants included; Azadirachta indica, Dodonaea viscosa, Lantana camara, Artemisia herba-alba, Ocimum basilicum, Nicotiana rustica and Solenostemma argel. Only leaves extracts were used from these plants, except for A. herba-alba the whole herb was extracted. Three concentrations (2.5 %, 5 % and 10 % w/v) from each plant extract were bio-assayed against the 3rd instar larvae of Trogoderma granarium, as a test insect. All botanical treatments showed positive dose related effects on the pest during various investigation periods. Comparison of the highest concentrations (10 %) among all plants showed no significant variations up to three days post exposure. Thenceforth, the ranking in a descending order showed A. indica on the top as the most effective plant, followed by O. basilicum, L. camara, N. rustica, D. viscosa, A. herba-alba and S. argel. No significant differences were found between 5 % and 10 % concentrations regarding S. argel, A. indica and O. basilicum. Moreover, the latter two plants induced 100 % mortalities within 18 days of treatments, preceding other plants, hence considered as the most effective of all tested species. These two plant species, plus L. camara, are recommended for further studies as potent sources of natural insecticides.