The study investigated the contact toxicity of powders made from rice husk ash, dry flower buds of Eugenia aromatica (L.) Baill., dry seeds of Piper guineense Schumach., groundnut pod shell ash, and leaves of Acanthus montanus (Nees) to eggs of five different grain storage moths: Plodia interpunctella (Hubner), Ephestia Keuhniella Zeller, E. elutella (Hubner) E. cautella (Walker) and Corcyra cephalonica (Stainton) at 25° C and 65% relative humidity. The powders were tested singly, and in binary and ternary combinations at the dosages of 0.0, 0.1, 0.2 and 0.4 g/10 g of grain in glass Petri dishes. The powders were mixed in equal proportions. The powders and eggs (1-2 days old) were mixed with grain. Egg eclosion and possible progress in larval development were observed 7 and 25 days post treatment, respectively. The highest eggs hatchability and larval development ratings was recorded in the controls. Irrespective of powder type, dosage and moth species, egg eclosion generally occurred. E. aromatica powder generally prevented egg hatch and larval development more effectively than other powders. The binary and ternary combination of E. aromatica powder with others similarly prevented eggs hatch and larval development. It can be concluded that there is great prospect in exploiting the lethality to storage moth eggs, of botanical powders like E. aromatica powder or its combination with other powders in the mitigation of damage to grain by these insects.
Keywords: Lethality, plant powders, moth eggs
