RESUMEN
Biological and Phytochemical studies were conducted on Atriplex semibaccata to investigate the biologically active compounds of this plant against Aphis craccivora Koch. Results indicate that, fraction A with LC[50 0.036] mg/cm[2] and LC[95 0.096] mg/cm[2] was the most effective against Aphis craccivora in comparison to fractions B and C as well as the crude extract itself. The LC[50] and LC[95] values of the crude extract were 0.057 and 1.523, respectively. However, the corresponding values for fraction B were 0.047 and 0.161 and for fraction C were 0.04 and 0.097, respectively. Data also showed that these fractions consist mainly of fatty acids and their esters, terpenes and hydrocarbons. Fraction A, which is the most potent fraction consists of fatty acids with percent area 32.028, esters [41%], terpenes [11.977%] and hydrocarbons [6.095%]. Fraction C followed fraction A according to the effectiveness against Aphis craccivora. It contains hydrocarbons with percent area 24.103, fatty acids 20.610%, fatty acids esters 24.378% and terpenes 3.865%. On the other hand, fraction B had the lowest toxicity compared with the other two fractions while; it was more toxic than the crude extract. It contains methyl salicylate with percent area 9.535% and phytol 7.00% in addition to the amount of fatty acids esters [6.406%] and high amount of hydrocarbons [53.405%]