Evaluation of the efficacy of some plant leaf extracts on insect pest infestation, growth and yield of water melon in Okigwe Southeastern Nigeria.

Abstract

Field experiments were carried out at the National Horticultural Research Institute, Okigwe, Imo State during the late cropping of 2012 and was repeated at the same cropping season in 2013 to evaluate the efficacies of some ethanol plant leaf extracts namely: garlic ( Allium sativum ), Neem ( Azadiracta indica), Ocimum gratissimum, Moringa olifera and tithonia on the insect pests of cucumber. The treatments consisted of three levels of concentration of each of the five extracts namely 50%, 75% and 100% as well as distilled water, concentrated water and synthetic insecticide cypermetrine at12.5% E.C. There were eighteen treatments for each season which were replicated three times in a split-plot experimented design. Results of the studies showed the identified commonest insect pest of the crop in the 2012 and 2013 cropping seasons to include flea beetles ( Cerotoma ruficornis ), cucumber beetle, Leptoglossus autralis and Diabrotica spp . The results also demonstrated that all the tested plant extracts at bi-weekly spraying interval were efficacious in controlling the insect pests. The efficacy of Allium sativum at 100% concentration was highest of all the plant extracts where 0.84kg/plot and1.05kg/plot were recorded in 2012 and 2013 seasons respectively. This was followed by 100% concentration of Azadirachta indica , 100% ocimum , 100% Moringa olifera and tithonia in that order. The efficacy of the cypermethrine (synthetic insecticidial check) was highest having performed best. Significant difference (P < 0.05) existed between the untreated (control) and all the treated plots in insect population and yield. However, the tested plant extracts at the three different concentration of 50%, 75% and 100% in both seasons proved efficacious in the control of the insect pests of cucumber as78.2% reduction in insect population, 79/8% reduction in leaf damage and 79.3% marketable fruit number were recorded in 2012 and 82.7% reduction in insect population, 76.4% reduction in leaf damage and 85.9% marketable fruit number in 2013 cropping season.