Perforation index assessment of cowpea seeds against cowpea bruchid, Callosobruchus maculatus (Fabricius) [Coleoptera: Chrysomelidae], infestation using Piper guineense

• Published in: Journal of basic & applied zoology 2020-10, Vol.81 (1), p.1-10, Article 60
• Main Authors: Ileke, Kayode David, Adesina, Jacobs Mobolade, Nwosu, Luke Chinaru, Olagunju, Abimbola
• Format: Article
• Language: English
• Subjects: Adult mortality; Bioactive compounds; Biomedical and Life Sciences; Entomology; Insecticidal activities; Leaves; Life Sciences; Seeds; Zoology; β-Pinene
• ISSN: 2090-990X; 2090-990X
• DOI: 10.1186/s41936-020-00195-7

Background Powders and extracts of Piper guineense seeds and leaves were assessed for insecticidal activities against Callosobruchus maculatus in the laboratory at temperature and relative humidity of 29.6 °C and 75.9%, respectively. Bioactive compounds in P . guineense leaves and seeds were also investigated. The powders were tested at rates 1.0, 2.0 and 4.0 g/20 g cowpea seeds while extracts were tested at 1.0, 2.0 and 3.0%. Results Results of contact toxicity assay of the seed powder caused 100% adult mortality at 96 h post-treatment period whereas leaf powder evoked 90% adult mortality within the same period at concentration of 1.0 g/20 g cowpea seeds. Low adult emergence was observed on cowpea seeds treated with 1 g of seed powder with percentage adult emergence of 10.0% and inhibition rate (IR) of 97.5%. Beetle Perforation Index (BPI) obtained from treated cowpea seeds was significantly different ( P < 0.05) from BPI of untreated seeds. Extracts of P . guineense seed were more toxic than seed powder. Piper guineense seed extract caused 87.5% adult mortality of C . maculatus while leaf extract caused 70.0% adult mortality within 24 h of infestation at concentration of 1%. Progeny development of C . maculatus was completely inhibited in cowpea treated with 2% and 3% leaf and seed extracts of P . guineense . β-Pinene was the most abundant active compound in P . guineense seed (55.6%) and leaf (48.4%). β-Phellandrene occurred 38.2% in seeds while Ocimene had the least value of 0.2% in seed and 0.5% in leaf. Conclusion The study showed that P . guineense seed powder and extracts were more effective than leaf powder and extract. Utilization of plant products as alternative to synthetic insecticides in protecting cowpea seeds against C . maculatus should be encouraged for enhanced food safety and security. Piper guineense is used as spice and medicine and interestingly safe for human use.