Toxicity of gaseous ozone to the different life stages of cowpea beetle, Callosobruchus maculatus (Coleoptera: Bruchidae), under laboratory conditions

Summary The cowpea beetle, Callosobruchus maculatus (Fabricius), is recognized as a common insect pest of cowpea worldwide. The present study aimed to evaluate the insecticidal activity of ozone gas against all life stages (egg, larva, pupa and adult) of C. maculatus at a concentration of 600 ppm (1.2 g/ m3) after 6 exposure times of 0.5, 1, 2, 3, 4 and 5 h under laboratory conditions. The mortality percentages of all life stages were significantly increased with increasing exposure time. Similarly, longer exposure time to ozone caused higher reduction of adult emergence from eggs, larvae and pupae. Treatment with ozone for 5 h caused egg mortality of 72.3%. Total mortality of adults was observed 5 days after treatment with ozone for 0.5 h. Moreover, treatment with ozone for 5 h resulted in 75, 100 and 94.1% reductions in adult emergence from eggs, larvae and pupae, respectively. The results also indicated that the larvae and adults were more susceptible to ozone gas than the eggs and pupae. Based on the findings, ozone showed promising insecticidal activity against all stages of C. maculatus and could be used as potential fumigant for management of this insect.