The insecticidal activity of some extracts and oils of some tropical plants against the yam moth <i>Euzopherodes Vapidella</i> Mann (Lepidoptera: Pyralidae)

Abstract

The ethanolic extracts and oils of eight tropical plants were evaluated under laboratory conditions for their relative toxicities to the eggs and larvae of the yam moth, Euzopherodes vapidella Mann. Contact toxicity of the extract and oil on the eggs and larvae of the yam moth was tested by treating 15g of Dioscorea alata measuring (4cmx4cmx1.5cm) with 0.5ml and 0.1ml of ethanol and oil extract in separate Petri dishes. This represents 3.3 and 0.6% concentration respectively. Each treatment was replicated three times. Each Petri dish containing the treated yam slice was infested with freshly laid eggs of E. vapidella on one hand and 15 third instar larvae on the other hand. Petri dishes containing the eggs and the larvae were left inside the insect-breeding cage until adult emergence. Ethanolic extract of Aframonmum melegueta Schum and Thonn; Eugenia aromatica Baillion; and Zingiber officinales Rosco were able to inhibit egg hatch and adult emergence. E. aromatica and Z. officinales were also able to prevent adult emergence when treated 4 days before eggs were introduced. The effect of ethanolic extract on larvae of E. vapidella at an application rate of 0.6 and 3.3% were low since there was no significant difference (P > 0.05) when compared with the control. The effect of oil extract was greater in the slices protected with Monodora tenuifolia and there was no egg hatch and adult emergence. The oil extracts from Arachis hypogaea and Elaeis guineensis had 20.0% and 13.3% adult emergence and there were significant differences (P < 0.05) when compared with the control which had 66.7% adult emergence. The oil can be applied on bruises or wound in yam tubers. Key Words: Ethanolic extract, tropical plants, Euzopherodes vapidella, toxicity, hatchability Ife Journal of Science Vol.6(1) 2004: 10-13