Effect of mating on the toxicity of rosemary (Rosmarinus officinalis) essential oil against the cowpea seed beetle (Callosobruchus macullatus)

The cowpea weevil beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae), is a major pest of legumes, especially cowpea , and has become a serious pest in storage crops. Therefore, controlling this insect pest using natural pesticides such as plant essential oils seems necessary. In this research, the effect of insect mating on the toxicity of rosemary essential oil against the cowpea weevil was investigated under laboratory conditions. Bioassay tests were performed in the range concentrations of 35.07 and 78.63 µl/lair for male virgin insects and 39.17 and 102.22 µl/lair for female virgin insects and there were done 55.04 to 86.49 and 62.90 to 94.36 µl/lair for one-time mated insects, respectively. Also, concentrations of 62/51 to 125.81 and 94.36 to 157.26 µl/lair were tested against multiple times mated male and female insects, respectively. Results showed that multiple mated male and female insects had the highest resistance to rosemary essential oil and the LC50 values were 90.032 µl/lair and 118.015 µl/lair for male and female insects, respectively. Virgin insects were more sensitive to rosemary essential oil and the amount of LC50 obtained was 48.173 µl/lair for male insects and 58.298 µl/lair for female insects. These results can be useful in planning pest management strategies for the cowpea weevil beetle by plant essential oils as well as the exact time of application of these compounds to achieve maximum effectiveness.