Effect of Crude Extract from Sweet Flag on Insecticidal, Anti-oviposition and Growth Inhibition of Diamondback Moth, Plutella xylostella (L.) (Lepidoptera : Yponomeutidae)

Abstract

The objective was to study effect of crude extract from sweet flag on insecticidal, anti-oviposition and growth inhibition on the 4^th instar larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera : Yponomeutidae). The various concentrations of crude extract from sweet flag 0.125, 0.25, 0.5, 1.0 and 2.0% (w/v) were applied. The study of insecticidal and growth inhibition used ten larvae of diamondback moth. Each concentration was replicated for five times. The 0.125% concentration was used as the anti-oviposition and released 20 pairs/cage of adult of diamondback moth and replicated for three times.  The treatments were arranged in a completely randomized design (CRD) and were conducted at laboratory of biology at temperature (25-27°C) and RH (75-80%). The results were found that the crude extract from sweet flag as insecticidal, anti-oviposition and development on  4^th larvae of diamondback moth was significantly effective (p<0.05) when compared with the control group. At 2.0% of crude extract from sweet flag was effective as insecticidal on 4^th larvae of diamondback moth. The percent of mortality was the highest 76.0 and 96.0% and LC₅₀ value with 0.75 and 0.25% at 24 and 48 h. The anti-oviposition, at 2.0% of crude extract from sweet flag was effective as insecticidal on 4^th larvae of diamondback moth. The mean number of egg was 2.00 + 0.81 eggs (95.31%) and the concentration of 0.125, 0.25, 0.5 and 0.1% was 45.31, 59.37, 71.87 and 80.47% at 48 h, respectively. Besides, at 0.125% of crude extract from sweet flag was 32.0% of mortality of pupa stage when compared with control group was 2.0%. The time of development of pupa stage and adult stage were 7.80 + 0.74 and 10.60 + 0.47 days, respectively when compared with control group were 4.60 + 0.80 and 6.20 + 0.74 days, respectively.