Larvicidal and Biochemical Effects of Ipomoea carnea (Convolvulaceae) Methanolic Leaf Extract Against Spodoptera frugiperda (Lepidoptera: Noctuidae) Under Laboratory Conditions

The larvicidal and biochemical effects of Ipomoea carnea Jacq. (Convolvulaceae) methanol leaf extract against the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) were determined under standard laboratory conditions. The second and fourth instar larvae of S. frugiperda were fed on castor bean leaves (Ricinus communis) treated with different concentrations (1–5%) of I. carnea methanolic leaf extract. The mortality percentage significantly increased in correlation with both concentration and exposure time compared to control. Second instar larva of S. frugiperda was more susceptible to this extract than the fourth instar, with LC50 values of 0.968% and 1.052%, respectively. Castor bean leaves treated with 5% extract and fed to second and fourth larval instar caused 96.3 and 92.9% larval mortality, respectively. Results from the biochemical analysis of larvae treated with I. carnea methanolic leaf extract revealed a significant reduction in total content of carbohydrate, protein and lipid compared to control. I. carnea methanolic leaf extract induced significant inhibition of acetylcholinesterase, α-esterase and β-esterase activities, alongside increase in peroxidase activity compared to the control groups. The current results are consistent with neurophysiological disruption and activation of oxidative stress in the treated S. frugiperda larvae. Therefore, we recommend I. carnea methanolic leaf extract for controlling S. frugiperda. Further field investigation into the efficacy of I. carnea methanolic leaf extract against S. frugiperda and the non-target organisms was required.