Field evaluation of crude extracts of Petiveria alliacea and biosynthesized silver nanoparticles against insect pests of Amaranthus caudatus (Lin.) and their effects on nutritional quality of Amaranthus leaves

Abstract

An environmentally friendly approach against field insect pests on crops is of enormous significance and has, over time, constituted a point of interest to crop protectionists. We conducted this experiment to compare the effectiveness of crude extracts from Petiveria alliacea and silver nanoparticles biosynthesized by P. alliacea against field insect pests of Amaranthus caudatus (Lin), and their impact on the proximate and mineral contents of the harvested leaves of Amaranthus. Silver nitrate was used in the biosynthesis of AgNPs by P. alliacea leaf (PaL-AgNPs) and root (PaR-AgNPs), with maximum absorbance ranging from 5.95 to 76.91 nm in size. Two synthetic insecticides (Dichlorvos and Cypermethrin) and untreated plots were included in the experiment. Each of the treatments was arranged in a randomized complete block design with three replications. Data collected were analyzed using analysis of variance (ANOVA). The findings showed that the two insects that were tested, Pygomorpha vignaudii and Phyllotreta striolata, were killed by crude extracts of P. alliacea and AgNPs. However, the insecticidal effect of Pa-AgNPs against P. vignaudii was more pronounced than the crude P. alliacea extracts. Meanwhile, PaR-AgNPs had the highest insecticidal efficacy (59 %) compared to crude P. alliacea extracts and PaL-AgNPs against P. striolata. Although none of the tested botanical and nano-insecticides was as effective as cypermethrin, they competed effectively with dichlorvos. Harvested Amaranthus leaves from plants treated with crude P. alliacea root exhibited the highest proximate contents (38.3 %), and those treated with PaR- and PaL-AgNPs yielded the highest mineral content (278.3–319.7 mg/100 g). Both Pa-AgNPs and crude extracts of P. alliacea did not have negative effects on the proximate and mineral contents of the harvested Amaranthus leaves. Therefore, the management practice of A. caudatus can incorporate the use of nano and botanical insecticides in the management of leafy vegetables, particularly in the organic farming system.