Sunthorn Pipithsangchan, Sanan Subhadhirasakul and Rapintara Yongwanitcha

pp. 1341 - 1349

Abstract

Studies on repellency effects of fractions from Thiem n-hexane extracts comprising n-hexane, chloroform, ethyl acetate and methanol fractions compared with Thiem n-hexane crude extracts were conducted under laboratory and field conditions. Five concentrations at 10,000 25,000 50,000 75,000 and 100,000 mg/L were tested in the laboratory. The statistical analysis for effective concentration at 50% (EC₅₀) of chemical repellency were done at 3, 6, 9, 12, 24, 36 and 48 hours after application. The results showed the concentration at 10,000 25,000 50,000 and 75,000 mg/L were not statistically different in their repellency of melon fly, but differed at the concentration of 100,000 m/L. Any fraction that the crude n-hexane extract
was given the best results, 68.43 percentage and the n-hexane fraction was 48.12 percentage at 48 hours. It was assumed that the non-polar solvent could take effect better than polar solvent and it was a contact repellent form. The EC₅₀ of Thiem n-hexane extract and n-hexane fraction were 27,260 and 77,841 mg/L, respectively, at 48 hours. The result of effective repelling melon fly of crude n-hexane extract and n-hexane fraction were tested in field conditions when spraying the extracts on a table. The results show that all concentrations crude n-hexane extract at after EC₅₀ (27,200 mg/L) would giving a good result in the second week and n-hexane fraction mixed with Latron CS-7 with having concentration at EC₅₀ (77,841 mg/L)
would giving a good result in third week.

Keywords

• repellency effects
• melon fly
• Bactrocera cucurbitae Coq. Diptera : Tephritidae
• Thiem n-hexane extracts