Biological activity of methanolic extracts of Ipomoea murucoides Roem et Schult on Spodoptera frugiperda J. E. Smith.
This study was carried out to assess the biological activity of methanolic extracts and fractions from Ipomoea murucoides [Roem et Schult (Convolvulaceae)] on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). The extracts were incorporated into a meridic diet in 2 mg mL-1 and fed to 1st instars larvae of S. frugiperda and incubated at 27°C with a photoperiod of 16:8 (L:D) h. After 7 days, surviving larvae were counted and weighed; surviving pupae were incubated until moths emerged, sexed and females allowed to lay eggs on paper foil. Fecundity was measured. The crude leaf extracts produced up to 46.16% mortality with effects on development, reduction in larval weight to 42.26 mg in 3rd instar and 59.6% in 5th instar, increased time for pupation and in reaching the adult stage; there was no effect on number eggs laid. The LC50 calculated for methanolic leaf extract had a value of 2.692 mg mL-1. The partially purified fractions showed no toxicity toward S. frugiperda, but had the highest effect on larval weight reduction, to 76.3% in 3rd instar and 74.6% in 5th instar, increased time for pupation and time to reach adult stage and had an effect on number eggs laid. These results indicate that the tested compounds delayed larval development.