Evaluations of toxicity, antifeedant, growth-regulatory activity of the methanol extract of Gliricidia sepium leaves were carried out against Dysdercus koenigii Fabr. (Heteroptera: Pyrrhocoridae), Achaea Janata Linn, and Spodoptera litura Fab., (both Lepidoptera: Noctuidae). Topical application of 100-300 μg of the extract to different stages of the test insects resulted in dose-dependent effects including larval-pupal intermediates and deformed adults. The highest tested dosage (300 μg/ μl) resulted in reduced survival rate and morphological abnormalities. At certain doses a strong antifeedant activity was evident against the lepidopteran insects.

The effect of a 2-month infestation by the cassava mealybug (Phenacoccus manihoti Mat. Ferr.) on the metabolism of nitrogen (amino acids) and carbon (carbohydrates), leaf area and total dry weight of five cassava varieties (Manihot esculenta Crantz), faux-caoutchouc (a hybrid of M. esculenta and M. glaziovii Muell, Arg.), poinsettia (Euphorbia pulcherrima Wild) and talinum (Talinum triangulare Jack) was studied. Free amino acid and free sugar contents as well as relative free amino acid composition in the leaf extracts, although found to be very different from one plant to another, were not significantly modified by P. manihoti infestation, except for the total amino acid contents of the cassava variety 30M7. Variations in one particular amino acid induced by mealybug infestation were not linked to the antibiotic resistance of these plants. Infestation by the cassava mealybug did not modify the total dry weight but reduced the total leaf area although this reduction was only significant in cassava varieties 59M2, 30M7 and M'pembe, and in faux-caoutchouc. Within the genus Manihot, the reduction in leaf area was strongly correlated (r= -0.878, P≤0.05) to the degree of antibiotic resistance and was coupled to an increase in the ratio of sugars to amino acids, suggesting a similarity between the effects of water stress and those of mealybug infestation.