Effects of Moringa oleifera Leaf Extract on Morphological and Physiological Growth of Cassava and its Efficacy in Controlling Zonocerus variegatus

Abstract

This work was carried out to study the effect of Moringa oleifera leaf extract (MLE) on the morphological and physiological growth characteristics of cassava (Manihot utilissima Pohl.); and its efficacy as organic insecticide for controlling Zonocerus variegatus infestation on the plant. The leaf extract was diluted in water at the ratios of 1:10, 1:20, 1:30 and 1:40. "Uppercut ^(R)” (30g dimethoate + 250g cypermethrin), used as water emulsifiable concentrate, was applied at the rate of 0.2 a.i./ha for comparison. Cassava hybrid, CR1247 was planted at the spacing of 1m x 1m. Moringa oleifera leaf extract was applied weekly while the dimethoate + cypermethrin was applied at three-weekly interval for two months. The experiment was laid out in a randomized complete block design (RCBD) with four replications. The Moringa oleifera leaf extract (MLE) dilution at the ratio of 1:30 MLE in water gave the highest percentage stem height difference (% SHD) at the eighth week after treatment with a value of 20.5% followed by 1:20, 1:10 MLE in water, dimethoate + cypermethrin and 1:40 MLE in water (i.e. 17.82%, 10.56%, 8.98% and 8.05% respectively). The control had the least % SHD. Dimethoate + cypermethrin had the highest percentage leaf number difference (% LND) at the eighth week after treatment with a value of 70.99% followed by 1:10, 1:30, 1:20 and 1:40 MLE in water in that order (i.e. 25.23%, 18.43%, 3.83% and 0.33% respectively). Control also had the least % LND. The 1:40 MLE in water treatment recorded the highest percentage leaf appearance (31%) at eight weeks followed by 1:30, 1:20, 1:10 and dimethoate + cypermethrin in that order (i.e. 29%, 28%, 26% and 20% respectively).  Dimethoate + cypermethrin 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 sixth week after treatment.