Concentration effects of chili and ginger extracts against diamondback moth (Plutella xylostella L.) on round cabbage

Abstract

Diamondback moth (Plutella xylostella L.) is a major pest of cabbage and other vegetables in the Brassicaceae family. The management and control of this cosmopolitan and economic pest has been a challenge in tropical regions. Reliance on chemical insecticides have led to resistance, natural enemy suppression, contaminated residues, risks to chemical poisoning and other environmental contamination. Therefore, the need to utilize non-host spice plants is an alternative. For this study, we focus on different concentration levels of two local spice plants; (1) chili (Capsicum frutescens L.) and (2) ginger (Zingiber officinale R.). Based on previous studies, extracts from both plants have been able to reduce pest infestation in vegetables. There were nine (9) treatments (T): T1=3ml of chili extract L−1 v/v, T2=6ml of chili extract L−1 v/v, T3=9ml of chili extract L−1 v/v, T4= 3ml of ginger extract L−1 v/v, T5= 6ml of ginger extract L−1 v/v, T6= 9ml of ginger extract L−1 v/v, T7=3ml of pure water L−1 v/v, T8=6ml of pure water L−1 v/v and T9=9ml of pure water L−1 v/v. From these treatments, 6ml chili was effective in lowering the defoliation (%) and was able to produce high leaf area index (LAI) regardless of increasing rainfall. Ginger 9ml produced high LAI and low defoliation in spite of increasing rainfall. Rainfall (mm) was an important environmental factor affecting the abundance, LAI and defoliation.