Potentiality of Fractionated Extracts from Hemizygia welwitschii Rolfe-Ashby (Lamiaceae) Leaf to Protect Maize against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in Storage

Abstract

Laboratory tests were conducted in order to assess the potential insecticidal effect of hexane, acetone and methanol fractionated extracts from Hemizygia welwitschii leaves against Sitophilus zeamais Motschulsky, important stored maize pest. The three extracts used individually were applied at four different concentrations (2, 4, 6 and 10 g/kg of maize) against the weevil. The efficacy of the treatment was evaluated by recording adult mortality after 1, 3, 7 and 14 days of infestation, and the F1 progeny emergence. Population increase, grain damage, and seeds germination were also assessed after three months of storage. The results showed that, among the three fractionated extracts, hexane extract was the most effective with 100% mortality recorded within 14 days after infestation at the concentration of 10 g/kg of maize, followed by acetone extract with 83.75% and methanol extract with 79.21% of mortality. The LC50 values decrease with the increase of exposure periods. The 14-day LC50 values were 0.78 g/kg, 1.58 g/kg and 3.10 g/kg respectively for hexane, acetone and methanol extract. The three extracts achieved significant inhibition of F1 progeny at all the concentrations. Among them, the hexane and methanol extracts induced complete inhibition of F1 progeny emergence at 10 g/kg of maize, acetone extract recorded 82.33% of inhibition. Significant reductions of insect population growth and percentage of seed damage were recorded after three months of storage on the maize treated with each extract at all the concentrations compared to negative control. Furthermore, no alive insects was recorded in maize seeds treated with the three extracts at the concentration of 10 g/kg. It is noticed that, percentage of gain damage were similar (0.15%) in maize treated with hexane and methanol extracts at 10 g/kg, while acetone extract recorded 0.76% of grain damage. In general, these extracts had no negative effect on the germination capacity of maize grains at the end of storage. Overall, the results obtained indicate that the use of these fractionated extracts could serve as an alternative to synthetic insecticides.

Olfactory Stimulants Mediated Egg-Laying Preference of Cowpea and Faba Bean Beetles and the Effectiveness of some Aromatic Plant Products as Protective Agents

“…Ignacimuthu et al, (2000) and Mainali et al, (2015) demonstrated that C. chinensis females employ chemical information during both host-seeking and acceptance. Also, results in the present study coupled with those by (Babu et al, 2003Beck et al, 2012Li et al, 2012) (Fotso et al 2018) or volatile oils (Fotso et al (2019) of Hemizygia welwitschia also significantly reduced the production and inhibited F1 progeny emergence of C. maculatus. Also, volatile oils of the Lamiaceae, Ocimum canum (Kosini et al, 2015) and Plectranthus glandulosus (Danga et.al., 2015) offer a significant reduction in seed damage activity compared with the untreated seeds.…”

“…Also, results in the present study coupled with those by Chudasama et al (2015), Kosini and Nukenine (2017) and Mahama et al (2018) suggest that leaf powder extracts are highly effective in controlling bruchids infestations. Hertlein et al (2011) and Fotso et al (2018) demonstrated that, effective control of protectants is attributed to the mortality of adult and/or immature stages, confirmed by lack of progeny generation. According to Fotso et al (2019) the efficacy of these botanical methods could be attributed to the presence of some bioactive compounds, including phenolic compounds, alkaloids, saponins, tannins, flavonoids, triterpenoids, and sterols.…”

The Mortality Effect of Some Plant Powders on the Cowpea Beetle, Callosobruchus maculatus Fab. (Coleoptera: Chrysomelidae)

“…It was reported that P. guineense had the highest larvicidal effect and lower productivity. Also, a study by Fotso et al (2018) investigated the efficacy of Hemizygia welwitschii leaf powders against C. maculatus and Sitophilus zeamais in stored cowpea and maize. The use of plant materials for grain preservation, particularly against cowpea beetle C. maculates is considered to be a promising alternative to synthetic insecticides (Boeke et al, 2004).…”

Insecticidal activities of long pepper (Piper retrofractum Vahl) fruit extracts against seed beetles (Callosobruchus maculatus Fabricius, Callosobruchus chinensis Linnaeus, and Sitophilus zeamais Motschulsky) and their effects on seed germination

“…The hexane extract from goat weed ( Ageratum conyzoides ) showed insecticide activity against coleoptera pests of stored products with LD 50 of 2.72–39.71 mg⋅g −1 , but ethanol extract ( Moreira et al., 2007 ). Fotso et al. (2020) revealed that all the tested Hemizygia welwitschii leaf extracts exhibited insecticidal action against maize weevil, which was more susceptible to the hexane extract than acetone extract.…”