Effects of <i>Moringa oleifera</i> leaf extract on morphological and physiological growth of cassava and its efficacy in controlling <i>Zonocerus variegatus</i>

Abstract

Zonocerus variegatus infestation has been found to cause a lot of devastation in the production of cassava crop plants in tropical and subtropical areas. Understanding the efficacy of Moringa oleifera leaf extract on controlling Z. variegatus is desired. The present study was conducted in the Department of Crop Science experimental site, Faculty of Agriculture, University of Nigeria, Nsukka to investigate the effects of M. oleifera leaf extract (MLE) on the morphological and physiological growth characteristics of cassava (Manihot utilissima Pohl.); and its efficacy as organic insecticide for controlling Z. variegatus infestation. M. oleifera leaf extract diluted in water at the volume to volume (v/v) ratios of 1:10, 1:20, 1:30 and 1:40 were applied weekly while “Uppercut ^(R)” (30 g dimethoate plus 250 g cypermethrin), used as water emulsifiable concentrate, was applied at the rate of 0.2 a.i./ha at three-weekly interval for two months. Result shows that M. oleifera leaf extract (MLE) dilution at the ratio of 1:30 MLE in water gave the highest percentage stem height difference (%SHD) at 32 weeks after planting with a value of 20.5% followed by 1:20 (17.8%), 1:10 (10.56%), dimethoate plus cypermethrin (8.98%) and 1:40 (8.05%). The control had the least %SHD and %LND. Dimethoate plus cypermethrin treatment was more efficacious as it eradicated the insects and caused significant (p < 0.05) increase in the number of leaves and reduction in the percentage leaf abscission especially from the thirtieth week after planting. However a combined use of Dimethoate plus cypermethrin and M. oleifera leaf extract may give a better result and as such recommended than a single treatment application.