Effect of four essential oils, including eucalyptus leaf, eucalyptus flower, rosemary leaf, and mint leaf on hatching and larval duration of the cowpea weevil

In this study, the fumigant toxicity of four essential oils, including eucalyptus leaf, eucalyptus flower, rosemary leaf, and mint leaf, was determined on the eggs (with less than 24 h) and the life span of the cowpea weevil (Callosobruchus maculatus). The results showed fumigant toxicity of these essential oils on the eggs in a dose-dependent manner showing the higher embryo mortality and the lesser hatching rate. Mint essential oil had the highest toxicity against the eggs with the 3.3% of eggs hatchability. Mint essential oil also increased the larval duration from 23.6 days in control to 27 days; however, the essential oils of eucalyptus leaf, eucalyptus flower, and rosemary showed no significant change in the larval duration as the survived embryos could complete larval stages in the equal time (statistically) with control. The use of herbal essential oils, especially mint essential oil, is very effective in controlling the cowpea weevil at the egg stage, and those may be a good substitute for common pesticides in warehouses.