Efficacy of Piper guineense Schumach. seed powder in the control of Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae: Bruchinae) and on the nutritional and organoleptic characteristics of stored cowpea Vigna unguiculata (L.) Walp.

Abstract

Brown pepper (Piper guineense) seed powder, used for culinary and medicinal purposes, was evaluated in the laboratory with a conventional storage chemical, actellic 2% dust (Pirimiphos-methyl), as standard, to protect stored cowpea against the cowpea bruchid, Callosobruchus maculatus. Four rates of the seed powder were used (2.5, 5.0 and 10.0 g/100 g seed with a control, 0.0 g) while actellic dust was applied at 1.0, 2.0, 3.0 g/100 g seed and 0.0 g/100 g seed as control. Data on percentage mortality, oviposition, adult emergence and seed damage were collected over a six-month period. Weevil perforation indexes (WPI) were estimated with the seed damage data. All data were analysed for variance at P≤0.05. Actellic dust at the lowest dose inflicted adult mortality (90 – 100%) in the first 48 h after treatment and prevented oviposition (95 – 100%) in the first five months of storage compared to the control. The highest rate of Piper guineense application caused mortality of up to 90.0% in 48 h, reduced oviposition (70 – 80%), decreased adult emergence (15.90 to 28.40 insects) as against the control (104.7 – 272.7 insects) and reduced seed damage by 80 % with a WPI of between 33.3 and 10.0 %. Proximate analysis and germination tests indicated that the treatment materials increased the moisture and crude fibre content, decreased crude protein content but had no significant effect on the viability of stored seeds. Organoleptic tests demonstrated that treatment materials had no significant negative effect on taste, odour, texture, appearance and overall acceptability of cooked cowpea seeds after six months of storage. It can be safely concluded that the powdered form of P. guineense seed at the highest doses (5.0 and 10.0 g) gave significant protection of cowpea seeds against the cowpea bruchid, which compared favourably with actellic dust when applied topically.

INSECTICIDAL ACTIVITY OF STEM BARK AND POD OF LOCUST BEAN (Parkia biglobossa) AGAINST COWPEA WEEVIL (Callosobruchus maculates F.) CAUSING DAMAGE IN STORED COWPEA

“…However, 3g of stem bark gave 100 % germination as against the control (93.33 %), suggesting that seeds can be stored for planting purposes. This result is in consistent with earlier works of Frank et al (2018) who reported the effect of Denettia tripetala F. and Okoye and Ebeledike (2013) who reported the effect of Mondora myristica (Gaertn.) Dunal on seed germination after storage for some period.…”

“…The reduction in numbers of eggs could be related to the early of mortality of some female or morbidity seen on male C. maculatus. The present finding is in line with that by Frank et al (2018) who reported that, Piper guineense performed better when compared with the control which he attributed to high mortality of C. maculatus that could not oviposit. Table 3 showed the effect of stem bark and pod powder on adult emergence and percentage adult emergence deterrence of C. maculatus.…”