Conventional insecticides are expensive and arguably associated with various severe adverse side effects hence the need to develop botanical pesticides that are effective as alternative. Though S. incanum fruits sap has been used by the local farmers to control aphids, literature show no scientifically investigated report of its effectiveness and the mode of its insecticidal action. This study was therefore designed to evaluate anti-aphids properties of crude fruit sap extract of S. incanum. A total of 180 kales were planted in the Plant Transformation Laboratory of Kenyatta University. They were divided into six groups with 10 plant stands each. Each group was subjected to routine spray with 10, 25, 50 and 75% S. incanum extract. Dimethoate was utilized as reference insecticide while the last group was not sprayed. The number of live and dead aphids was counted for two weeks after every pray in each group with an interval of one day to determine the deterrent and insecticidal activity. The extract at different tested concentrations showed some level of insecticidal and deterrent activities against green peach aphid. Further, phytochemical screening results showed that the crude fruits sap extract of S. incanum have phytochemicals associated with insecticidal and deterrent activity. The study has established that the crude fruits sap extract of S. incanum are effective in managing insects’ pest.