REVIEW PAPER BIOLOGICAL CONTROL OF APHIDS IN WHEAT FIELDS

1.Economic importance Wheat is the most important cereal crop in Egypt. It is constrained by a varei-ty of insect pests, vertebrates and diseases. Aphids are the serious insect pests at-tacking wheat plants in Egypt, their losses to the crop were estimated by 7-23% in middle and upper Egypt, where highest infestation mostly occurs (Enayat et al., 1984; Tantawi 1985b; El-Heneidy et al., 1991). Aphids are one of the insect groups whose economic importance increases with the development of agriculture. The ex-tensive monoculture and agrotechnical practices result in much better conditions for population increase than the aphids find in natural environments. Pesticide treatme‌nts against various pests have been followed by the occurrence of secondary pests and the aphids are agreed as belonging mainly to this group. The intensification of pesticide treatment has shown that the aphids cannot be eradicated but, on the con‌trary, resistant populations have appeared which exhibit even more vitality than the original sensitive strains. Besides, the routine pesticide treatments have adversely influenced the natural enemies population. 2.Aphids Damage Aphids cause direct damage to plants by sucking plant fluid and also cause in‌direct damage as vectors of economically important virusus. The cereal aphids are efficient vectors of different strains (types) of Barley Yellow Dwarf Virus (BYDV), which has recently been identified as economically serious in some parts of Egypt (Abou El-Ata et al., 1995). 3.Aphids Species on wheat El-Hariry, 1979, Tantawi, 1985 a,b and El-Heneidy and Attia, 1988 recorded