Insecticidal activity of Poppy (Papaver somniferum L.) seed oil against cowpea weevil (Callosobruchus maculatus F.) in stored cowpea

Abstract

In this study, the insecticidal effect of Poppy (Papaver somniferum) seed oil was investigated against Callosobruchus maculatus (Bruchidae) in cowpea, at different concentrations and exposure time. The Poppy seed oil at 2, 4, 6, 8 and 10 ml/kg was tested against adults of C. maculatus, and the mortality was counted after 24, 48 and 72 h of exposure. All tests were conducted at 27–30 °C and 65 ± 5% r.h. The experiments were carried out based on the factorial experiment by randomized complete design with four replications. Twenty-five insects with 0–24 h old were used for each replication. The effect of Poppy seed oil on the reduction of emergence of insects in next generation (F1) was also assayed. The results of experiments indicate the significant differences between concentrations and exposure time (p < 0.0001), and the increase of concentrations and exposure time increased mortality. The amount of mortality at high concentrations was remarkable, and highest mortality rate (96.91%) was recorded at 10 ml/kg, after 72 h of exposure. The application of oil significantly reduced F1 progeny production and even at lowest concentration (2 ml/kg), the amount of F1 production was reduced more than 70%, compared with control treatment. Complete (100%) reduction in progeny production was recorded at the rates of 8 and 10 ml/kg. The results of seed germination assay showed no significant differences between control and treated seed, and no harmful effect was observed on the seed germination. These results proved that Poppy seed oil can be used as a controlling agent of storage pests, especially C. maculatus, although more detailed studies are necessary.