The cowpea aphid; Aphis craccivora is one of the harmful pests, which infest cowpea bean, Faba bean plants and many crops leading to a decrease of crop production. Plants including; Citrullus colocynthis, Peganum harmala, Senna alexandrina, andApium graveolens wereextracted bymethanol 70%, in order to evaluate its toxicity effect on Aphis craccivora in laboratory and field, as well as Alkaline phosphatase, non-specific esterase and mixed-function oxidase were evaluated after treatment with LC₅₀ of different plant extracts. The results showed that LC₅₀ was 4890.079,5537.761, 6118.4856 and 6118.4856 ppm respectively, while it was 74.1996 ppm for Pirimicarb. Moreover, the combination of the different plant extracts showed or exhibit such a dramatic reduction in A. craccivora in the field and minimize the concentration of the pirimicarb required to reduce the aphid population in the field. Also, P. harmala, S. alexandrina showed an increase in Alkaline phosphatase, non-specific esterase and mixed-function oxidase, while it was moderate for C. colocynthis and low for A. graveolens compared with the control. These results should be helpful in the rational applications of insect pest management.