Insecticidal Effects of Some Plant Leaf Extracts in the Control of Insect Field Pests of Amaranthus hybridus L

Abstract

A field trail was conducted at the Botanical garden of department of Plant Science and Biotechnology, Abia State University, Uturu, Nigeria to assess the insecticidal effect of aqueous leaf extracts of Azadirachta indica, Ocimum gratisimum and Vernonia amygdalina on insect field pests of Amaranthus hybridus. The experimental design was randomized complete block with three replicates. Aqueous leaf extracts of the powdered samples of these plants were uniformly sprayed on the experimental material at 30 g/l twice weekly from 10 to 38 days after sowing. A. hybridus plants sprayed with aqueous leaf extracts of the different plants had lower percentage leaf and leaf area damage compared to the control. Percentage leaf damage followed this order: A. indica < V. amygdalina < O. gratisimum < control, with percentages leaf damage of 25-27%, 34-46%, 32-49% and 47-73%, respectively. Percent leaf area damage were 18.6%, 31%, 45.8% and 61.2% for A. indica, O. gratisimum, V. amygdalina and control, respectively. Significantly (P<0.05) higher plant height, root length and dry matter production were obtained in plants sprayed with aqueous leaf extract of A. indica in contrast to the other treatments, which had comparable values with the control. The results indicate that A. indica if properly harnessed can be used as a biopesticide in the control of insect field pest of A. indica .

Evaluation of Biorational Insecticides as Stand-alone Treatments for the Management of the Pigweed Flea Beetle, Disonycha glabrata (Coleoptera: Chrysomelidae), in Organic Production of Amaranthus spp.

“…Despite these achievements, their use has become a serious global concern due to the high toxicity to humans and a disruption in ecosystem processes (Showler, Greenberg, & Arnason, 2004;Overall, 2008). Biorational insecticides cause less environmental harm while providing effective management of crop pests (Showler et al 2004;Overall, 2008;Leskey, Lee, Short, & Wright, 2012;Laznik & Trdan, 2017;Iwuagwu et al, 2019;Muralikrishna et al, 2019). The results from this study confirm the effect of OMRI-approved insecticides in the management of D. glabrata.…”

“…oz.) and the economic status of many small growers, use of Azatin O will become financially prohibitive for many limited resource growers and an unsatisfactory outcome (Iwuagwu et al, 2019;Muralikrishna et al, 2019). The manufacturer's label indicates that Azatin ® O is more effective in suppressing larval or nymphal insect stages (not adults) which may, at least in part, explain the poor performance recorded for adults in this study.…”

“…In some cases, to mitigate losses growers use synthetic insecticides as the management tactic of choice to control pests such as the lepidopteran defoliator, Spoladea recurvalis, Fab. (Family: Crambidae) often with varying level of success (Sufang et al, 2013;Iwuagwu, Ogbonna, & Okechukwu, 2019;Muralikrishna, Mathew, Paul, & Nithya, 2019). However, the use of synthetic insecticides as a plant protection measure not only remains controversial but is also highly restricted in organic production of leafy and other vegetables.…”

“…washing) prior to cooking or in salads (Rastogi & Shukla, 2013). Biorational insecticides provide of a safer, effective and sustainable insect pest management plan for organic production of amaranth as it leaves minimal negative footprints in the ecosystem (Korrat, Abdelmonem, Helalia, & Khalifa, 2012;Sufang et al, 2013;Iwuagwu et al 2019). Biorational insecticides obtained from leaves and flowers (e.g.…”

“…Saccharopolyspora spinosa, Bacillus thuringiensis) are known to be effective in the management of insect pests on leafy vegetables, including lepidopteran defoliators on Amaranthus spp. (Cordero, Kuhar, Speese, & Barlow, 2005;Nuessly, 2005;Flanery, Sintim, Dingha, & Jackai, 2016;Iwuagwu et al 2019;Muralikrishna et al, 2019). Given their range of activity across insect taxa, we there is a good chance that biorational insecticides hold great promise for management of D. glabrata.…”