Diamondback Moth (Plutella xylostella L.) Control on Chinese Kale by Application of Plant Extracts

Abstract

Extracts of five plant species were evaluated for insecticidal activity against the second and third instar larva of diamondback moth (DBM), Plutella xylostella L., by a leaf dipping method. Ageratum conyzoides leaf extracts showed maximum insecticidal activity followed by Chromolaena ordorata leaf, Stemona curtisii roots, Curcuma longa rhizomes and Morinda coreia leaf extracts, respectively. Their LC50 valves at 72 hours against the second instar larva were 584.4, 841.6, 1,009.0, 1,165.1 and 2,010.0 ppm, respectively, and those against the third instar larva were 1,351.0, 1,785.3, 1,808.8, 2,353.4 and 3,807.5 ppm, respectively. Field trials were conducted to evaluate the efficacy of A. conyzoides leaf extracts against DBM on Chinese kale in the dry season (JanuaryFebuary 2006) and The rainy season (August-September 2006). The experiments were arranged in a randomized complete block design with five treatments and four replications. Treatments consisted of (1) untreated control (2) the extracts at concentration of 1 % (3) the extracts at concentration of 3 % (4) the extracts at concentration of 5 % and (5) abamectin. In the dry season, A. conyzoides leaf extracts at The concentration of 5 and 3 % exhibited good satisfactory control of DBM and gave no difference compared to abamectin which was the most effective. However, there was no statistically significant difference among treatments in rainy season. It is concluded that A. conyzoides leaves extracts have high potential for practical application as natural insect control agent.