Preparation of plant extracts: Aqueous plant extract was prepared by sun-drying for 2 days and grinding separately 100 g of fresh leaves of each of the selected plants in a blender following Abd El-Khair and Haggag (2007) method. Resultant extract solution was filtered through two layers of cheesecloth and different concentrations prepared by diluting 1 part of the plant extract into 9 part of sterile distilled water.