Insecticidal activity of Muntingia calabura extracts against larvae and pupae of diamondback, Plutella xylostella (Lepidoptera, Plutellidae)

AbstractThe aim of the present study was to evaluate the insecticidal effects of hexane and ethanolic extracts of the flowers and fruits of Muntingia calabura against diamondback moth, Plutella xylostella. The leaf disc immersion methodology was carried out to assess the insecticidal effects on the larvae and pupae as well as duration of the larval phase following feeding of the first instar larvae of diamondback on the treated leaf discs for 72 h. All extracts were toxic to larvae and pupae of P. xylostella. The ethanolic extracts of the flowers and fruits of M. calabura were the most toxic against first instar P. xylostella larvae with LC50 values of 0.61 μg mL−1 and 1.63 μg mL−1 respectively, followed by the hexane extract of the fruits (LC50 = 5.5 μg mL−1) and flowers (LC50 = 18.9 μg mL−1). All extracts were more toxic to P. xylostella larvae compared with cordycepin, the positive control which produced 100% mortality at 500 μg mL−1 in 72 h. Fruit extracts were more active than the flowers in producing pupal mortality following 72 h of feeding of the first instar larvae on leaf discs treated with the extracts. Both the hexane and the ethanolic extracts of M. calabura fruits and flowers prolonged larval duration by ∼2 days in some cases as compared with the control (7.2 days). These results suggest that M. calabura has potential for development as commercial insecticide for controlling P. xylostella due to its insecticidal effects