The experiments were conducted in laboratory conditions of a temperature of 25± 2C and relative moisture of 40± 5 % to evaluate the effectiveness of the cinnamon, lavender and clove essential oils on some biological life aspects of cowpea beetle, C. maculates. Results of the obligative experiment for the effect of the oils on insect adult killing showed that the concentration of 5% caused a mortality percentage averaged 13.33% of the insect males. The mortality percentage of the insect females was 11.3% for the cinnamon and lavender oils. The lavender oil had the lowest effect on adult killing, not exceeding 0. For the effect of the oils on egg laying, clove oil affected the number of eggs highly at the concentration of 5%, resulting in 2.00 eggs on average. The lowest oil effect on egg number was for the lavender oil at the concentration of 1%, leading to an average of 14.73 eggs. The clove oil at the concentration of 5% showed effectiveness in adult emergence prevention as it was not observed that any insect emerged.
In contrast, the same oil at the concentration of 1% had less effect, resulting in the highest emergence percentage reaching 13.33%. The same applies to the effect of the plant oils on insect productivity as the clove oil at the concentration of 5% was the most effective; no insect productivity was recorded, unlike the concentration of 1%, recorded productivity of 110.2 %. In the facultative experiment, the highest mortality percentage was recorded using clove oil against females, as the mortality percentage reached 4.00%. In contrast, the lowest mortality percentage was recorded using lavender oil against males, where no killing occurred, as the mortality percentage did not exceed 0.00%. For the effect of the oils on egg laying, the highest affected oil was cinnamon at a concentration of 5% as the number of eggs reached 5.60, while lavender oil at 3% was the least effective; the average number of eggs was 25. Clove oil at a concentration of 5% had the highest effect in reducing the emergence of the insect, so the emergence percentage did not exceed 0.33%. In comparison, its influence was low at 1%, recording the highest emergence percentage (18.67%). The lowest recorded insect productivity average was from the treatment of the clove oil at a concentration of 5%, which did not exceed 5.20%, while the highest productivity average was from the treatment of the lavender oil at 1%, which reached 89.6%.
Keywords: essential oils, Cowpea beetle, Callosobruchus maculatus
