Suntorn Pipithsangchan, Sanan Subhadhirasakul, Sujirat Sritangnanta, and Aran Ngampongsai

pp. 121 - 135

Abstract

Studies on repellency and anti-oviposition effects of Thiem-seed oil and Thiem-seed crude extract on melon fly (Bactrocera cucurbitae Coq.) were carried out under laboratory and field conditions. Five concentrations of the oils and the crude extract at 50, 100, 150, 200 and 300 g/L were tested in the laboratory.
Effective concentration at 50% (EC₅₀) and effective time at 80% (ET₈₀) of repellent and anti-oviposition actions were calculated using probit analysis at 1, 4, 8, 12, 24, 36 and 48 hours after application. The results show that the repellent and anti-oviposition actions on the melon fly of the Thiem-seed oil were better than those of the Thiem-seed crude extract. At 24 hours, the EC₅₀ for the repellent and the anti-oviposition actions of the oil were 10.86 and 7.80 g/L, whereas those of the crude extract were > 100 and 21.70 g/L, respectively.
At the concentration of 300 g/L (30% W/V), the ET₈₀ of the repellent and the anti-oviposition actions of the oil were 23.23 hours and 38.01 hours, whereas those of the crude extract were 5.14 hours and 13.86 hours, respectively. In the field study, the results show that the cucumbit fruit damage due to the melon fly was equal at 43.3% in the plots treated with the oil and in those treated with crude extract at the concentration of 15% (W/V) after 5 days of application. The fruit damage was high at 73.3% in untreated plots. The application
of the oil and the crude extract mixed with 10% (W/V) surfactants, Latron^® CS-7 and Foil^®, provided a reduction in fruit damage ranging from 46.2% to 61.4% as compared to the application of the oil and the crude extract alone.