Oviposition Deterrence and Ovicidal Activity of Birbira (Melletia furrgunia) on Diamondback Moth (Plutella xylostella) (Lepidoptera: Plutellidae)

The efficacy of different polar and non-polar solvent extracts of Birbira, Melletia furrginea (Hochst.) Baker tree seeds namely: Water, Acetic acid, Acetone, Chloroform, Toluene, and Hexane at different rates were evaluated on Diamondback moth, Plutella xylostella L. oviposition and egg mortality under laboratory conditions. The leaf dipping method was used to run both assays. In the assay, full Oviposition deterrence was recorded at the higher rates of polar solvent extracts. Significantly higher egg un-hatchability was recorded only at the higher rates for non-polar extracts. Eggs mortality caused by extracts with Water and Acetone was very high, and have much smaller LC50 values. In contrast, LC50 was higher for the other extracts. However, there was a constant increase in the percent kill of egg mass with the increase in the extract concentration. From this study, it is evident that M. furrgunia extracts with different solvents possess significant oviposition deterrence and ovicidal effect on P. xylostella.

Biological activities and chemical composition of Mentha piperita and Syzygium aromaticum essential oil fractions against cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae)

Callosobruchus maculatus (Fabricius) is one of the major, common, pests of stored grains as it causes quantitative and qualitative losses in legume crops. This research sought to find the most active fraction in Mentha piperita and Syzygium aromaticum essential oils, to evaluate bioactivity of those crude essential oils and active fractions against C. maculatus, and to identify the compounds contained in the active fraction. The essential oils were fractionated using three solvents, namely n-hexane, ethyl acetate, and methanol. The n-hexane fraction was identified as the active fraction, causing mortality, oviposition deterrence, and ovicidal effects. In fumigation chambers, LD95 values of M. piperita (Mnf) and S. aromaticum n-hexane fractions (Snf) were 0.045 ml/l and 0.057 ml/l respectively. ED50 values for oviposition deterrence were 0.016 ml/l for Mnf and 0.022 ml/l for Snf. ED50 value of ovicidal effects for Mnf- and Snf-treated eggs were 0.014 ml/l for both fractions. GC-MS analysis showed 8 dominant compounds in Mnf and 5 dominant compounds in Snf. Overall it is concluded that Mnf and Snf oils have effective biological activities against stored pest C. maculatus and have potential to be considered as alternatives to synthetic insecticides.

Electrophysiological, Behavioural and Biochemical Effect of Ocimum Basilicum Oil and Its Constituents Methyl Chavicol and Linalool on Musca Domestica L.

The Ocimum basilicum essential oil (EO) was evaluated for its biological effect on M. domestica. Characterization of O. basilicum EO revealed the presence of methyl chavicol (70.93%), linalool (9.34%), epi-α-cadinol (3.69 %), methyl eugenol (2.48%), γ-cadinene (1.67%), 1,8-cineole (1.30%) and (E)-β-ocimene (1.11%). The basil EO and its constituents methyl chavicol and linalool caused the neuronal response in female adults of M. domestica. Adult female flies showed reduced preference to food source laced with basil EO and methyl chavicol. Substrate treated with EO and methyl chavicol at 0.25% caused an oviposition deterrence of over 80%. The ovicidal effect was high in O. basilicum EO (EC50 9.74mg/dm3) followed by methyl chavicol (EC50 10.67mg/dm3) and linalool (EC50 13.57mg/dm3. On contact toxicity, adults exposed to EO (LD50 10.01 μg/adult) were more susceptible than to methyl chavicol and linalool (LD50 13.62 μg/adult and LD50 43.12 μg/adult respectively). EO and its constituents methyl chavicol and linalool induced the detoxifying enzymes Carboxyl esterase (Car E) and Glutathione S – transferases (GST)

Effects of Cantharidin and Norcantharidin on Larval Feeding and Adult Oviposition Preferences of the Diamondback Moth (Lepidoptera: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a destructive insect pest of cruciferous plants that has developed resistance to almost every listed commercial insecticide. Cantharidin as an animal-derived biopesticide is a natural defensive compound produced by Meloidae insects with toxicity to many insects including P. xylostella. Norcantharidin is an important substitute of cantharidin and has similar insecticidal activities to cantharidin. Although the toxicity of cantharidin and norcantharidin to P. xylostella has been reported, little research has focused on the effects of cantharidin or norcantharidin on the behavior of P. xylostella. In this study, we investigated the feeding behavior of third-instar larvae and the oviposition preference of adult P. xylostella in order to explore the effects of different concentrations of cantharidin and norcantharidin. Results show that cantharidin and norcantharidin have antifeedant effect on P. xylostella larvae. The values for AFC50 were 13.0228 and 149.4210 mg/ml, respectively. Furthermore, the oviposition deterrence rate of cantharidin on P. xylostella ranged from 49.37 to 58.24% and that of norcantharidin was from 20.88 to 33.33%. These results suggest cantharidin and norcantharidin may have repellent and antifeedant effect on P. xylostella, which could contribute toward using biopesticides to manage P. xylostella and may provide a new strategy for integrated pest management.