The Repellent and Antioviposition Effects of Crude Root Extracts ofStemona curtisii Hook. F., Derris elliptica Benth. And Thiem Seed Kernel Oil (Azadirachta excelsa (Jack) Jacobs.) on Diamondback Moth (Plutella xylostella L.)

Abstract

This research was aimed to test the insect repellency and antioviposition effect of crude root extracts of Stemona curtisii, Derris eliiptica and Thiem seed kernel (Azadirachta excelca) oil on Diamondback moth. The root of Stemona curtisii and Derris elliptica were extracted by maceration using methanol as the extracting solvent. The tests of insect repellency and antioviposition effect of different concentrations of crude extracts showed that crude extract from S. curtisii gave better protection than D. elliptica. The crude extracts concentrations from S. curtisii and D. elliptica that could repel 50% of insects (EC₅₀) at the 48^th observed hour were 2,683.6 and 48,075.8 mg/l respectively, whereas the crude extract concentrations from S. curtisii and D. ellptica that could reduce 50% of the insects’ antioviposition (EC₅₀) at the 48^th  observed hour were 24.9 and 80.0 mg/l respectively. Antioviposition activities of root extract of Thiem seed kernel at 500,000 mg/l concentration against Diamondback moth adults in laboratory conditions were tested from a distance of 1-4 m for periods of time up to five days. Both root extracts and oil extract of Thiem seed kernel showed antioviposition effects on the Diamondback moth, although the effect declined with distance and time. The oil extract of Thiem Seed Kernel showed the highest antioviposition activity over a distance of 2 m for 3 days, while the antioviposition activities of S. curtisii extract and D. ellipatica extract were 2 m for 2 day and 1 m for 1 day respectively. The efficacy of crude extract of S. curtisii, D. elliptica and oil extract of Thiem seed kernel in reducing antioviposition of Diamondback moth were tested by spraying these extracts on a cost of black gusset placed over chisin planted in a hydroponics field. The results showed that oil extract of Thiem seed kernel gave the best antioviposition activity, followed by S. cuttusii and D. elliptica extract.