Entries on Botany
The book Weed-Crop Interactions examines the approaches used to study competition in natural and managed ecosystems. It provides information on importance of competition on mixed cropping systems, and weed suppression in mixed planting systems. Information has been provided on microbially produced phytotoxins that exist in nature and the considerable interest in using either the organisms themselves or the chemicals they produce to suppress weed growth, as naturally produced herbicides.
ABSTRACT: The leaf extracts of Draceana aborea and Vitex doniana of Agavaceae and Verbenaceae families respectively, were tested on the larvae of anopheles mosquito for their botanical insecticidal effects. The results of the investigation showed that the minimum percentage mortality concentration (MPMC) of these leaf extracts on the test organisms were at 7 5ml/20ml and 10ml/20ml as the start ng po nts for D. aborea and V. doniana, respectively. Findings equally revealed that the combination of D. aborea and V. doniana leaf extracts exerted synergistic effects on these organisms at 5.0ml/20ml, whereas the use of the D. aborea and V. doniana extracts separately resulted in reduced efficacy. Analysis of variance showed that, there was no significan difference (P = 0.01) between the synergy and the individual treatments of the leaf extracts on these organisms. Preliminary phytochemical screening showed the presence of flavonoids, free phenolics, condensed tannins, pseudo anins, triterpenes, glycosides and saponins which have some insecticidal effects on their targeted organisms. These findings represent one of the steps in identifying plants, with insecticidal properties from the rich Bioresources in the Mosaic of the LowLand Rainforest vegetation zone of Southeastern Nigeria.