http://www.eje.cz Citrus tristeza closterovirus (Closterovirus: Closteroviridae) (Ayazpour et al., 2013). Chemical control is the main method used to control citrus aphids (Smaili et al., 2014). However, excessive use of insecticides reduces natural enemy populations and leads to resistance of the aphids to many common insecticides. Biological control is a safe alternative method for controlling aphids in citrus orchards (Alizadeh Kafeshani et al., 2018).Scymnus syriacus Marseul (Coleoptera: Coccinellidae) is a widely distributed species and is important in suppressing aphid abundance in citrus orchards (Allawi, 2006). Both larvae and adults actively search for leaves infested with aphids. They feed on many species of aphids, especially A. spiraecola and A. gossypii (Emami et al., 2004). The young larvae of S. syriacus usually suck out the contents of aphids, whereas adults eat the whole body of the aphids. The number of aphids consumed depends on the size of the aphid, developmental stage of the predator and environmental conditions, such as temperature. The mean number of aphids consumed by the larval stages of S. syriacus has reported to be 95 and 130 aphids at 25°C and 30°C, respectively (Allawi, 2006).