ABSTRACT Survey and relative densities of L. trifolii and its parasitoids were studied on three faba bean cultivars in newly reclaimed sandy land at El-Salhia district, Sharkia Governorate Egypt during 2015 / 16 and 2016/17 growing seasons. The obtained results were summarized as follows: 1. The faba bean leafminer infestation on faba bean cultivars started in the 3rd week of November in the first and second seasons. It continued till the end of both seasons. 2. Two tested cultivars; Giza 716 and Giza 3 were highly susceptible to the pest infestation while, Giza 843 cultivar was less susceptible to the pest infestation. The mean numbers of larvae / sample for the three cultivars were 140.45, 127.23 and 110.77 &147.57, 123.24 and 115.33 in the first and second seasons, respectively. Statistical analysis revealed that the differences between three cultivars were significant and highly significant (F= 7.537* and 16.607**) during 2015 / 16 and 2016/17 seasons, respectively. 3. The mean percentages of infestation in the first season were 77.95, 76.36 and 67.91% on Giza 716, Giza 3 and Giza 843, respectively. They were 75.05, 74.19 and 67.05 % in the second season, respectively. 4. In the first season, means of mines/ sample for Giza 716 , Giza 3 and Giza 843 were 202.59, 188.77 and 181.86, respectively. While in the second season 214.19, 181.38 and 177.57 were recorded, consecutively. 5. Eleven hymenopterous parasitoid species, of L. trifolii belonging to Eulophidae, Braconidae and Pteromalidae were recorded. They included four ecto-larval, three endo-larval and four endo-larval –pupal parasitoids. 6. Generally, the most dominant ecto-larval parasitoid was Diglyphus isaea (Walk.), accounting for 24.65 and 30.10% of the total recorded parasitoids in the first and second seasons, successively. It was followed by endo-larval parasitoids, Neochrysocharis formosa (West.) Which composed 21.42 and 17.35% of parasitoids in the first and second seasons, respectively? Opius basalis Fischer was the most abundant endo-larval - pupal species which parasitized 11.02 and 10.90 % of the pest larvae in the first and second seasons, consecutively. 7. The parasitoids of L. trifolii on faba bean cultivars had four to six peaks annually. The mean parasitism percentages of the host larvae were 66.38, 63.24 and 57.78 & 61.97, 65.39 and 54.30% on Giza 716, Giza 3 and Giza 843 in the first and second seasons, respectively. 8. Temperature and relative humidity affected infestation percentages by 22.29, 31.37 and 22.41% & 23.12, 15.75 and 17.09% during 2015/16 and 2016/17 seasons, respectively. While their influences on percentages of parasitism were 15.89, 15.76 and 6.28% & 16.84, 42.06 and 14.66% during two seasons, respectively. 9. The chemical contents affected on the infestation percentages by L. trifolii infested three faba bean cultivars. Key words: Liriomyza trifolii, Faba bean, Relative densities, Parasitoids, Parasitism, Biological control.