Esters are among compounds produced in industries all over the world and regarded as significant products due to their application in the production of herbicides, pesticides, paints, solvents, and plastics. The most commonly used method of synthesizing esters is the Fisher esterification reaction. Fatty acids (caprylic, lauric, and palmitic) were reacted with polyethylene glycol (PEG 400 and PEG 600) to synthesize non-ionic surfactants, then they were elucidated by IR spectrum and mass spectrometry, and then their physico-chemical properties were estimated such as (HLB, CMC, free acidity or alkalinity and solubility). Physico-chemical characteristics of pesticide spray solution were estimated separately and after mixing with esters. After that, the 4th instar larvae of the cotton leaf-worm were treated with serial concentrations of the synthesized esters alone, recommended pesticide and also treated by LC50 of the pesticide with esters. Results showed that, the synthesized non-ionic surfactants were enhanced the physico-chemical characteristics of spray solutions. As a result of mixing pesticides with surfactants, pesticides' viscosity and conductivity increased while their surface tension and pH value decreased. The findings of the bioassay test also showed that all surfactants decreased the LC50 value of the insecticide Emamectin benzoate 1.9% EC, however adding PEG 600 MC to the pesticide had the best effects, lowering its LC50 value to 0.021 ppm. Thus, after the necessary investigation has been done on these esters, it is recommended to combine them with commercially recommended insecticides in order to decrease the amount of pesticide utilized and subsequently contamination of the environment.