Field experiments were conducted for evaluating site effect of two insecticides namely, dursban (Chlorpyrifos) and sumi-alpha (Es-fenvalerate) recommended for cotton bollworms by using three sprayer types, convention motor sprayer (A), penumatic knapsack motor sprayer (Solo) (B) and penumatic knapsack motor sprayer (Solo) contact with micronor (developed knapsack motor) (C) on certain piercing-sucking pests and associated predators in cotton fields at Zagazig region Sharkia Governorate, Egypt throughout seasons 2014 and 2015. The results indicated that the highest mean reduction in the tested insects population was noticed for both dursban and sumi-alpha treatments by using the conventional sprayer (A). The corresponding averages of reduction percentages during the two seasons, 2014 and 2015 were 74.98 and 75.54 % for aphids,74.61 and 81.28 % for white fly,80.78 and 90.30 % for leafhoppers and 55.93 and 80.36 % for mites incase of dursban treatment, whereas these values were 65.48 and 73.25% for aphids,79.84 and 82,39 % for whight fly, 77.47 and 87.32 % for leafhoppers and 54.06 and 73.16% for mites when sumi-alpha was applied during the two seasons; respectively. In regarding the harmful effect on the associated predators, the highest relatively initial reduction value were recorded in the predators populations in plots sprayed  by the two tested pesticides when C sprayer type was used, where the initial effect recorded 100 % for the two tested pesticides for all inspected predators species, except for Scymnus spp. and Chrysoprella carnea in sumi-alpha plots which recorded 97.00 and 90.60 % in the 1^st season and 97.32 and 93.60 % for the same predators species, respectively for dursban plots. In case of the mean of residual effect of the two tested pesticides on inspected predators species, the relatively highest reduction percentages ranged 93.45-96.95 % and 96.32-99.11 % in the population of Peaderus alfierii. and Coccinella spp. in plots applied with dursban by using C sprayer  in the 1^st  and 2^nd seasons, respectively