Biopesticidal Activity of Lunumidella (<i>Melia dubia</i>) Leaf Extract

Abstract

This study was conducted to investigate the pest controlling potential of two Melia dubia leaf extracts, namely aqueous extract (T1) and aqueous formulation prepared using the methanol extract (T2) to control pests such as thrips, mealy bugs, scale insects and caterpillars. Plant parts with pests were selected and the two prepared extracts were sprayed with a control (C). Five days after application, the Pest Mortality Percentage was recorded. The aqueous extract (T1) was applied for a period of four weeks with seven day intervals. The aqueous formulation prepared incorporating the methanol extract (T2) was applied in two concentrations as 50 g/L and 100 g/L. The aqueous formulation prepared using the methanol extract (T2) was highly effective against thrips, mealy bugs and caterpillars. The aqueous extract (T1) showed the highest Pest Mortality Percentage within two weeks of preparation but the activity decreased thereafter. The Pest Mortality Percentages resulted from the two methods were significantly different from each other and the higher percentage was shown by the aqueous formulation (T2). When the aqueous formulation (T2) was applied to the caterpillars in the cabbage cultivation, it showed a significant reduction in the number of caterpillars along with a reduction of the damage caused by the caterpillars to the cabbage leaves. The yields obtained from the treated beds with T2 were significantly higher than those obtained from the control beds. Even though the aqueous extract (T1) has short storage ability, it can be introduced to farmers as a biopesticide which can be prepared by their own for controlling pests in their crops. As the chemically extracted Melia dubia leaf powder which was used in the preparation of the aqueous formulation (T2) can be stored frozen for a long period retaining its bioactivity, there is great potential for improving it as a commercial product.