BIOASSAY STUDIES ON THE EFFECT OF ESSENTIAL OILS ON THE FEMALE ORIENTAL FRUIT FLY, Bactrocera dorsalis (Hendel) (DIPTERA : TEPHRITIDAE)

Abstract

The semiochemical functions of essential oils extracted from four different plant materials viz., hinoki, eucalyptus, cinnamon and Litsea were investigated on  the females of Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). The GC-MS analysis showed that most identified volatile checmicals from the essential oils were monoterpene with low molecular weights, which included 6-octenal,3,7-dimethyl,(R) (tR= 21.35, 43.246%); 6-octen-1-ol,3,7-dimethyl (tR= 23.369, 9.02%); 4-hexen-1-ol,5-methyl-2-(1-methyletheny) (tR = 24.232, 17.714%); beta-phellandrene (tR=15.191, 12.616%); eucalyptol  (tR=17.439, 38.216%); (+)-4-carene  (tR= 26.82, 18.237%); 1,R-alpha-pinene (tR=13.875, 29.565%); limonene (tR=17.18, 19.042%) and fenchyl acetate  (tR=23.096,
10.798%). Bioassay studies on the effects of the essential oils showed that significantly more number of female adults of B. dorsalis alighted on filter paper treated with hinoki oil, (R)-(+)-limonene, and eucalyptus oil at 400ppm.  However, cinnamon was found to inhibit or repel alighting of the female adults at a dosage of 200ppm (p = 0.001), 400ppm (p = 0.0001) and 800ppm (p = 0.0001).  A similar repellent activity was observed when filter paper was treated with essential oils extracted from Litsea leaves.  The calculated preference showed that hinoki was the most preferred essential oil (50.91%), which stimulated the alighting response of B. dorsalis at 100ppm.