Larvicidal and feeding deterrent properties of extracts from Dieffenbachia maculata (Dumb cane) against Spodoptera frugiperda in maize (Zea mays)

Abstract

This study examined the larvicidal and feeding deterrent properties of extracts from Dieffenbachia maculata against Spodoptera frugiperda (Fall army worm) in growing maize. A 9 m x 7 m space in the green house was divided into forty-two plots of 1 m by 0.75 m with 0.5 m discard between rows. This is to allow for a 2 x 3 x 4 factorial experiment replicated three times. Maize seeds were sown at two seeds per hole at a spacing of 90 cm by 60cm in each plot. Each plot was barricaded with wire mesh to prevent the migration of larvae from plot to plot. The irrigation system in the greenhouse supplied equal volume of water at the base of the maize seedlings every morning. Infested maize plants were treated with different Dumb cane plant extracts at the concentration of 25ml/l and30ml/l along with positive and negative controls. (The positive control was treated with Cypermethrine at 3l/ha) to compare the effect of concentrations on the fall army worm activity. In this experiment, the numbers of leaves affected was assessed every week and recorded. Leave perforation index was calculated. Dead armyworms were observed by prodding the larvae for movement and were recorded. Plant vigour was obtained by measuring plant height and the number of leaves formed. Effect of the worm on yield was determined by comparing total yield from sampled maize plants and this was compared to expected yield from the variety of maize used for the research. The positive control group exhibited a significantly lower level of infestation after treatment with a corresponding yield increase, (16.06% and 80.14%) respectively when compared to the treated groups. Similarly, leave extract using acetone at 30ml record significantly better results with 17.73% level of infestation after treatment application and 66.44% yield increase. This was closely followed by leaf extract using methanol at 30ml with significantly lower level of infestation and increased yield respectively. (21.35% and 60.42%). Conversely, the lowest value was recorded for the negative control. Among the extract treatments, the leaf extract using acetone at 30ml showed the highest efficacy in reducing infestation levels and demonstrated the most significant increase in maize yield. In this study, it was observed that application of the 30ml leaf extract of Dumb cane using acetone was effective and significantly increased army worm larval mortality, reduced leaf damage, and increased maize grain yield compared to the untreated control. The results indicated that the extracts from dumb cane leaves and stems exhibited promising capacity in the control of Fall army worm in maize. Further research is warranted to optimize the application protocols and evaluate any residual effects of the extracts on maize grain and ecosystem dynamics