Contact Toxicity Effects of Selected Organic Leaf Extracts of Tithonia diversifolia (Hemsl.) A. Gray and Vernonia lasiopus (O. Hoffman) against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)
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Date
2021
Authors
Gitahi, Stephen Maina
Ngugi, Mathew Piero
Mburu, David Nganga
Machocho, Alex Kingori
Journal Title
Journal ISSN
Volume Title
Publisher
Hindawi
Abstract
Maize weevil (Sitophilus zeamais) infestation results in a substantial reduction in the quantity and deterioration of the quality of
stored maize. Most farmers control weevils using conventional pesticides which are usually associated with several human health
risks as well as intoxication of the fauna and flora. However, bioinsecticides form an alternative intervention since they possess
fewer side effects on human health, are ecofriendly, and are readily available. 'is study sought to validate and document, in a
systematic way, the pesticidal properties of the species Tithonia diversifolia and Vernonia lasiopus used for many years by many
people of the world on S. zeamais. 'e plant leaf samples were obtained from Embu County, Kenya. Dichloromethane and ethyl
acetate solvents were used to extract active phytochemicals from the dried plant sample powder. 'e GC-MS analysis of the
obtained extracts was performed at ICIPE laboratories to identify their phytochemical compositions. Twenty grams of maize
grains were put in 50 ml plastic vials and admixed with different treatments. 'e positive control group was treated with Actellic
Super™, while the negative control was treated with the respective extracting solvent only. 'e experimental groups were
separately treated with the plant leaf extracts at doses of 25, 50, 75, and 100%. After treatment, each of the six groups was infested
with 10 male S. zeamais and weevil mortality as a result of contact toxicity of the treatments was assessed at 6, 24, 48, 72, and 96
hours after the insects were exposed to the extracts. Results of the study indicate that the selected organic leaf extracts of
T. diversifolia and V. lasiopus possessed significant contact insecticidal effects that ranged between 1.67 to 99.98%. Furthermore,
the GC-MS analysis revealed several active biocompounds in T. diversifolia and V. lasiopus extracts, which are known for their
considerable insecticidal effects. Our data suggest that the organic leaf extracts of T. diversifolia and V. lasiopus have considerable
insecticidal properties and would, therefore, be a valuable bioprotective agent for stored maize grains against S. zeamais.
Description
A research article published in International Journal of Zoology
Keywords
Leaf Extracts of Tithonia diversifolia, Tithonia diversifolia, Vernonia lasiopus, S. zeamais, Embu County, Kenya
Citation
Gitahi, S. M., Ngugi, M. P., Mburu, D. N., & Machocho, A. K. (2021). Contact Toxicity Effects of Selected Organic Leaf Extracts of Tithonia diversifolia (Hemsl.) A. Gray and Vernonia lasiopus (O. Hoffman) against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). International Journal of Zoology, 2021.