Abstract: 【Aim】The cotton aphid,  Aphis gossypii Glover, is one of the most injurious pests of fruits, vegetables and ornamental plants worldwide, both outdoor and indoor. This insect, which feeds from plant sap, produces honeydew and transmits plant viruses, and causes quantitative and qualitative damages in plants. For controlling this pest in greenhouse, plant essential oils are used as an alternative to chemical insecticides. So in this research the fumigant toxicity of Carum copticum L. (Apiaceae) essential oil against A. gossypii adults was studied. 【Methods】 Dry ground seeds of C. copticum were subjected to hydrodistillation using a modified Clevenger-type apparatus. All bioassay tests were conducted at 27± 2℃, 65%±5% RH and a photoperiod of 16L:8D. This research was performed with a completely random design with 6 treatments (5 different concentrations of essential oils plus the control). Each concentration included 3 replicates and each replicate consisted of 20 adult pests. 【Results】 The results showed that the C. copticum essential oil caused significant mortality of adults 24 hours after exposure. The LC₅₀ value of the essential oil against  A. gossypii adults was 1.21 μL/L air. The mortality percentage of  A. gossypii showed higher sensitivity to application of the essential oil. The LT₅₀ value of this essential oil estimated for A. gossypii at the concentration of 1.21 μL/L air was 11.79 h. The fumigant toxicity of this essential oil had an ordered relationship with the concentration and time exposure. Results of GC/MS constituents showed that the essential oil consisted of 18 chemical compounds and most importantly included thymol (50.07%), gamaterpinene (23.99%), and p-cymene (22.90%). 【Conclusion】 The results suggest that  C. copticum essential oil has appropriate insecticidal effects on cotton aphids, which may have a promising potential to be used in the integrated pest management programs of pest insects in greenhouses.

Key words: Aphis gossypii, Carum copticum, essential oil, fumigant toxicity, gas chromatography/mass spectrometry